Semiconductor display device

ABSTRACT

To provide a semiconductor display device capable of displaying an image having clarity and a desired color, even when the speed of deterioration of an EL layer is influenced by its environment. Display pixels and sensor pixels of an EL display each have an EL element, and the sensor pixels each have a diode. The luminance of the EL elements of each in the display pixels is controlled in accordance with the amount of electric current flowing in each of the diodes.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an EL display that is formed byfabricating an EL (Electro Luminescence) element on a substrate.Particularly, the present invention relates to an active matrix type ELdisplay that uses a semiconductor element (an element employing asemiconductor thin film), and furthermore to a semiconductor displaydevice employing the EL display.

[0003] 2. Description of the Related Art

[0004] In recent years, technology for forming a TFT on a substrate hasbeen largely improved, and an application development of the TFT to anactive matrix type semiconductor display device has been carried out. Inparticular, the TFT using a polysilicon film has a higher electric fieldeffect mobility than the TFT using a conventional amorphous siliconfilm, and therefore, the TFT may be operated at a high speed. Thus, thepixel control which has been conducted at a driver circuit outside ofthe substrate may be conducted at the driver circuit which is formed onthe same substrate as the pixel.

[0005] Such an active matrix type semiconductor display device can, bypreparing various circuits and elements on the same substrate, obtainvarious advantages such as a decrease in manufacturing cost, a decreasein the size of the semiconductor display device, an increase in yield,and a decrease in throughput.

[0006] Further, research on the active matrix type EL display having anEL element as a self-light-emitting element is becoming more and moreactive. The EL display is referred to as a light-emitting display, anorganic EL display (OELD) or an organic light-emitting diode (OLED).

[0007] The EL display is a self-light-emitting type unlike a liquidcrystal display device. The EL element is constituted such that a layercontaining an organic compound (hereinafter, referred to as an EL layer)is sandwiched between a pair of electrodes (anode and cathode). However,the EL layer normally has a lamination structure. Typically, thelamination structure of a “hole transport layer/a light emittinglayer/an electron transport layer” proposed by Tang et al. of theEastman Kodak Company can be cited. This structure has a very highlight-emitting efficiency, and this structure is adopted in almost allthe EL displays which are currently subjected to research anddevelopment.

[0008] When the EL element obtains Luminescence (Electro Luminescence)which is generated by applying a voltage to the EL element, it iscomposed of an anode layer, an EL layer, and a cathode layer. There aretwo types of luminescence in an organic compound, one being aluminescence that is generated when the organic compound returns from asinglet excitation state to a ground state (fluorescence) and the otherbeing a luminescence that is generated when the organic compound returnsfrom a triplet excitation state to a ground state (phosphorescence).Either type of luminescence may be used in the EL display of the presentinvention.

[0009] In addition, the structure may be such that on the electrodes, ahole injection layer/a hole transport layer/a light emitting layer/ anelectron transport layer, or a hole injection layer/a hole transportlayer/a light emitting layer/an electron transport layer/an electroninjection layer may be laminated in order. Phosphorescent dye or thelike may be doped into the light emitting layer.

[0010] In this specification, all the layers provided between a pair ofelectrodes are generally referred to as EL layers. Consequently, thehole injection layer, the hole transport layer, the light emittinglayer, the electron transport layer, the electron injection layer andthe like are all included in the EL layers.

[0011] In this specification, a light emitting element, which iscomposed of an anode, an EL layer and a cathode, is referred to as an ELelement.

[0012] The deterioration of the EL material of the EL layer has become aproblem in the realization of the EL display, which leads to thereduction in the luminance of the EL element.

[0013] The EL material of the EL layer is inferior to moisture, oxygen,light, and heat, which are the factors that promote the deterioration ofthe EL layer. To be more specific, the rate at which the EL layerdeteriorates is influenced by the structure of a device driving the ELdisplay, characteristics of the EL material structuring the EL layer,materials of an electrode, conditions of the manufacturing processes, adriving method of the EL display and the like.

[0014] The EL layer deteriorates even if a constant voltage from a pairof electrodes is applied thereto, whereby the luminance of the ELelement is reduced. Thus, an image displayed on the EL display is notclear because of the reduction in the luminance of the EL element.

[0015] Further, Color display systems of the EL display are roughlydivided into four: a system where three kinds of EL elementscorresponding to R (red). G (green), and B (blue), respectively, areformed; a system where EL elements emitting white light are combinedwith a color filter; a system where EL elements emitting blue orblue-green light are combined with a fluophor (fluorescent colorconversion layer: CCM): and a system where EL elements corresponding toR, G, and B are superimposed on a transparent electrode used as acathode (an opposing electrode) (RGB stacking method).

[0016] The EL material that structures the EL layer differs depending onthe luminescing color of the EL layer. Therefore, in the color displaysystem that employs three kinds of El elements corresponding to thecolors R (red), G (green), and B (blue), the three kinds of EL elementsof the EL layer corresponding to RGB each may deteriorate at differentrates. In this case, the luminance of the EL elements that correspond toRGB becomes dissimilar, respectively, as time passes. Consequently, animage having a desirable color cannot be displayed on the EL display

SUMMARY OF THE INVENTION

[0017] The present invention has been made in view of the above, andtherefore has an object to provide an EL display capable of performing aclear and desirable color display by suppressing a reduction inluminance of an EL element even if an EL layer is deteriorated.

[0018] The EL display of the present invention has a sensor portion fordetecting a luminance of a portion for displaying an image of the ELdisplay (display portion) and revising the luminance to a desirablevalue. The sensor portion includes one or a plurality of pixels. It isto be noted that the pixel(s) of the sensor portion will hereinafter bereferred to as sensor pixel(s) throughout this specification.

[0019] The sensor pixel(s) is composed of an EL element and a lightreceiving diode that detects the amount of change in the luminance ofthe EL element. It is to be noted that throughout this specification,the EL element of the sensor pixel(s) will hereinafter be referred to asa sensor EL element.

[0020] The sensor EL element has the same structure as that of the ELelement (hereinafter referred to as display EL element) of the pixel(hereinafter referred to as display pixel) of the display portion. Atleast a material that constructs a pair of electrodes and a materialthat constructs a lamination structure of an EL layer and the EL layerare the same, respectively.

[0021] Then, a signal, which is the same as a signal inputted to anarbitrarily selected display EL element, is fed to the sensor ELelement. In this specification, the input of a signal to the EL element(display EL element and sensor EL element) means that an electricpotential of the signal is applied to one of the electrodes of the ELelement, and an EL drive voltage is applied to the EL layer. Here, theEL drive voltage is the electric potential difference between theelectric potential of the signal applied to one of the electrodes of theEL element and the constant electric potential applied to the otherelectrode thereof.

[0022] Thus, an equivalent voltage is applied to the EL layers of thesensor EL element and the arbitrarily selected display EL element,whereby the deterioration rates of the EL layers are nearly equivalent.Therefore, the luminance of the sensor EL element and the luminance ofthe display EL element maintain almost equivalent states even as timeelapses.

[0023] Light emitted by the sensor EL element, on one hand, isirradiated to the light receiving diode of the senor pixel. Then, thelight receiving diode detects the luminance of the sensor EL element. Onthe basis of the information of the luminance of the sensor EL elementthat was detected, the luminance of the display EL element is revised,and the luminance of the sensor EL element is also revised at the sametime.

[0024] By adopting the above structure, the present invention has madeit possible for the EL display to perform a clear and desirable colordisplay by suppressing the reduction in luminance of the EL element evenif the EL layer is deteriorated.

[0025] The EL display of the present invention may be of a color displaysystem that employs a display EL element emitting white light, or acolor display system that employs display EL elements corresponding tothe colors RGB, respectively. In case of the color display system thatemploys the display EL elements corresponding to each of the colors RGB,it is preferable that the senor pixels corresponding to each of thecolors RGB are provided in the sensor portion. However, the presentinvention is not limited to the structure thereof. It may be a structurein which the sensor pixels, which correspond to either 1 or 2 colors ofthe RGB colors, are provided in the sensor portion. In particular, it iseffective to provide the sensor pixel that corresponds to the color ofwhich the deterioration of the EL layer is remarkable in the sensorportion to thereby display an image having a desirable color.

[0026] It is further preferable that the display EL element and thesensor EL element are formed at the same time under the same conditions.The deterioration rates of the EL layers of the display EL element andthe sensor EL element can be made equivalent by adopting the abovestructure. Therefore, the luminance of the sensor EL element that willbe detected by the light receiving diode becomes equivalent with theluminance of the display EL element, to thereby detect the change in theluminance of the display EL element more accurately. Thus, it becomespossible to revise the luminance of the display EL element to adesirable value.

[0027] Furthermore, when the sensor portion is formed simultaneouslywith the display portion on the substrate, as the manufacturing processof the El display, only the process of forming the light receiving diodehas to be added to the manufacturing process in the case where thesensor portion is not provided. Therefore, there is no need toremarkably increase the number of-manufacturing processes, therebymaking it possible to suppress the number of manufacturing processes.

[0028] It is to be noted that a portion of the display portion may beused as the sensor portion. That is, among the pixels of the displayportion, one or a plurality of pixels that are arbitrarily selected maybe employed as sensor pixels and the rest of the pixels may be employedas display pixels. In this case, the size of the EL display can besuppressed because the space for the provision of the sensor portion canbe omitted compared with the case of not including the sensor portion inthe display portion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In the accompanying drawings:

[0030]FIG. 1 is a schematic diagram of the top of an EL display of thepresent invention;

[0031]FIG. 2 is a circuit diagram of an EL display of the presentinvention;

[0032]FIG. 3 is a circuit diagram of a sensor pixel of an EL display ofthe present invention;

[0033]FIG. 4 is a circuit diagram of a display pixel of an EL display ofthe present invention;

[0034]FIG. 5 is a timing chart when an EL display of the presentinvention is driven by a digital method;

[0035]FIG. 6 is a block diagram of a correction circuit of an EL displayof the present invention;

[0036]FIG. 7 is a schematic diagram of the top of an EL display of thepresent invention;

[0037]FIG. 8 is a timing chart when an EL display of the presentinvention is driven by an analog method;

[0038]FIG. 9 is a block diagram of a video signal correction circuit ofan EL display of the present invention;

[0039]FIGS. 10A to 10E are diagrams showing a process of manufacturingan EL display of the present invention;

[0040]FIGS. 11A to 11D are diagrams showing the process of manufacturingthe EL display of the present invention;

[0041]FIGS. 12A to 12C are diagrams showing the process of manufacturingthe EL display of the present invention;

[0042]FIGS. 13A and 13B are diagrams showing the process ofmanufacturing the EL display of the present invention;

[0043]FIG. 14 is a cross sectional diagram of an EL display of thepresent invention;

[0044]FIG. 15 is a circuit diagram of a sensor pixel of an EL display ofthe present invention;

[0045]FIG. 16 is a cross sectional diagram of an EL display of thepresent invention;

[0046]FIGS. 17A and 17B are external views of an EL display of thepresent invention;

[0047]FIGS. 18A and 18B are external views of an EL display of thepresent invention;

[0048]FIG. 19 is a cross sectional diagram of a display pixel of an ELdisplay of the present invention;

[0049]FIGS. 20A and 20B are a top view and a circuit diagram,respectively, of a display pixel of an EL display of the presentinvention;

[0050]FIG. 21 is a cross sectional diagram of a display pixel of an ELdisplay of the present invention;

[0051]FIGS. 22A to 22C are circuit diagrams of a display pixel of an ELdisplay of the present invention;

[0052]FIGS. 23A to 23F are diagrams showing examples of electronicequipment using an EL display of the present invention;

[0053]FIGS. 24A and 24B are diagrams of electronic equipments using anEL display of the present invention; and

[0054]FIG. 25 is a cross sectional diagram of an EL display of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0055] An embodiment mode of the present invention will be explainedwith reference to FIGS. 1 to 6.

[0056] Shown in FIG. 1 is a top view of an EL display, which is aportion of a semiconductor display device of the present invention. Itis to be noted that in the embodiment mode of the present invention, anexplanation will be made on an EL display for performing color displaythat is driven by a digital method. However, the driving method of theEL display of the present invention is not limited to the digitalmethod, and the EL display may be driven by an analog method. Inaddition, although an explanation is made in the embodiment mode on theEL display for performing color display, the EL display of the presentinvention may performs not only color display, but also monochromedisplay.

[0057] As shown in FIG. 1, there is provided a display portion 101, asource signal line driver circuit 102, a gate signal line driver circuit103, and a sensor portion 106. The source signal line driver circuit 102is composed of a shift register 102 a, a latch (A) 102 b, and a latch(B) 102 c.

[0058] The sensor portion 106 has sensor pixels 104 (R sensor pixel 104a, G sensor pixel 104 b, and B sensor pixel 104 c) that correspond tothe colors RGB, respectively. Note that an EL display of a color displaysystem that employs three kinds of EL elements corresponding to thecolors RGB is illustrated in the embodiment mode. However, the presentinvention is not limited thereto., and an EL display of a color displaysystem that employs an EL element emitting white light may be used.Further, in the embodiment mode, although the sensor portion 106 has 3sensor pixels that correspond to the colors RGB, respectively, thepresent invention is not limited thereto. Only sensor pixels thatcorrespond to 1 or 2 colors of the colors RGB may be provided in thesensor portion.

[0059] A detailed circuit diagram of the display portion 101 and thesensor portion 106 is shown in FIG. 2. Source signal lines (S1 to Sx),power source supply lines (V1 to Vx), and gate signal lines (G1 to Gy)are provided in the display portion 101. Note that the sensor portion106 and the display portion 101 are provided on the same substrate inthe embodiment mode. However, the present invention is not limitedthereto. The structure may be such that the sensor portion and thedisplay portion are provided on different substrates and connected by anFPC or the like.

[0060] The display portion 101 includes a plurality of display pixels105. The display pixels 105 each have any one of the source signal lines(S1 to Sx), any one of the power source supply lines (V1 to Vx), and anyone of the gate signal lines (G1 to Gy). There are 3 types of displaypixels 105: a display pixel for displaying the color R; a display pixelfor displaying the color G; and a display pixel for displaying the colorB.

[0061] A source signal line Sp (where p is an arbitrary number between 1and x), a power source supply line Vp, and a gate signal line Gq (whereq is an arbitrary number between 1 and y) are contained in anarbitrarily selected display pixel (p, q) of the display pixels fordisplaying the color R. Also, similar to the display pixel (p, q) fordisplaying the color R, the source signal line Sp, the power sourcesupply line Vp, and the gate signal line Gq are contained in the Rsensor pixel 104 a.

[0062] Though not shown in the figure, similarly, the same source signalline, power source supply line, and gate signal line that are includedin an arbitrarily selected display pixel for displaying the color G arealso contained in the G sensor pixel 104 b. Likewise not shown in thefigure, the same source signal line, power source supply line, and gatesignal line that are contained in an arbitrarily selected display pixelfor displaying the color B are also contained in the B sensor pixel 104c.

[0063] A detailed structure of the sensor pixels 104 a to 104 c is shownin FIG. 3. A region that is surrounded by a dotted line is the sensorpixel 104. Contained in the sensor pixel 104 are a source signal line S(any one of the lines between S1 and Sx), a power source supply line V(any one of the lines between V1 and Vx), and a gate signal line G (anyone of the lines between G1 and Gy).

[0064] In addition, the sensor pixel 104 (104 a to 104 c) has aswitching TFT 130, an EL driving TFT 131, and a sensor EL element 132. Acapacitor 133 is provided in the structure of FIG. 3, but the structuremay be formed without the provision of the capacitor 133.

[0065] The sensor EL element 132 is composed of an anode, a cathode, andan EL layer provided therebetween. When the anode is connected to adrain region of the EL driving TFT 131, in other words., when the anodeis a pixel electrode, the cathode serving as an opposing electrode isheld at a predetermined electric potential (opposing electricpotential). On the other hand, when the cathode is connected to thedrain region of the EL driving TFT 131, in other words, when the cathodeis the pixel electrode, then the anode serving as the opposing electrodeis held at a predetermined electric potential (opposing electricpotential).

[0066] A gate electrode of the switching TFT 130 is connected to thegate signal line G. One of a source region and a drain region of theswitching TFT 130 is connected to the source signal line S, and theother is connected to a gate electrode of the EL driving TFT 131.

[0067] One of a source region and the drain region of the EL driving TFT131 is connected to the power source supply line V, and the other isconnected to the sensor EL element 132. The capacitor 133 is provided soas to be connected to the gate electrode of the EL driving TFT 131 andthe power source supply line V.

[0068] Further, the sensor pixel 104 has a reset TFT 134, a buffer TFT135, and a light receiving diode 136.

[0069] A gate electrode of the reset TFT 134 is connected to a resetsignal line RL. A source region of the reset TFT 134 is connected to asensor power source line VB and a drain region of the buffer TFT 135.The sensor power source line VB is constantly held at a fixed electricpotential (standard electric potential). Further, a drain region of thereset TFT 134 is connected to the light receiving diode 136 and a gateelectrode of the buffer TFT 135.

[0070] A source region of the buffer TFT 135 is connected to a sensoroutput wiring FL. The sensor output wiring FL is further connected to aconstant-current power source 137 and a fixed current constantly flowstherein. Further, the drain region of the buffer TFT 135 is connected tothe sensor power source line VB which is constantly maintained at afixed standard electric potential. The buffer TFT 135 functions as asource follower.

[0071] Although not shown in the figure, the light receiving diode 136is composed of a cathode, an anode, and a photoelectric converting layerprovided therebetween.

[0072] Shown in FIG. 4 is a detailed structure of the display pixel 105.An area surrounded by a dotted line is the display pixel 105. The sourcesignal line S (any one of the lines between S1 and Sx), the power sourcesupply line V (any one of the lines between V1 and Vx), and the gatesignal line G (any one of the lines between G1 and Gy) are contained inthe display pixel 105.

[0073] Similar to the sensor pixel 104, the display pixel 105 has aswitching TFT 140, an EL driving TFT 141, and a display EL element 142.The display EL element 142 has the same structure as that of the sensorEL element 132 that is shown in FIG. 3. To be more specific, the displayEL element 142 and the sensor EL element 132 each have an EL layersandwiched between a pair of electrodes. In addition, the materialconstructing the pair of electrodes and the laminate structure of the ELlayer are at least respectively the same for both the EL elements. Inparticular, when the color of light emitted by the sensor EL element 132and the display EL element 142 is the same, then the material (ELmaterial) that forms the EL layer is also the same.

[0074] The display EL element 142 is composed of an anode, a cathode,and an EL layer provided therebetween. When the anode is connected to adrain region of the EL driving TFT 141, in other words, when the anodeis a pixel electrode, the cathode serving as an opposing electrode isheld at a predetermined electric potential (opposing electricpotential). On the other hand, when the cathode is connected to thedrain region of the EL driving TFT 141, in other words, when the cathodeis the pixel electrode, then the anode serving as the opposing electrodeis held at a predetermined electric potential (opposing electricpotential).

[0075] Further, a capacitor 143 is provided in the structure of FIG. 4,but the structure may be formed without the provision of the capacitor143.

[0076] A gate electrode of the switching TFT 140 is connected to thegate signal line G. One of a source region and a drain region of theswitching TFT 140 is connected to the source signal line S, and theother is connected to a gate electrode of the EL driving TFT 141.

[0077] One of a source region and the drain region of the EL driving TFT141 is connected to the power source supply line V, and the other isconnected to the display EL element 142. The capacitor 143 is providedso as to be connected to the gate electrode of the EL driving TFT 141and the power source supply line V.

[0078] Next, a description will be made on a driving method of the ELdisplay of the embodiment mode.

[0079]FIG. 1 is referenced. In the source signal line driver circuit102, a clock signal (CLK) and a start pulse (SP) are inputted to theshift register 102 a. The shift register 102 a sequentially generatestiming signals on the basis of the clock signal (CLK) and the startpulse (SP) to thereby sequentially feed the timing signals to downstreamcircuits.

[0080] The timing signals from the shift register 102 a arecurrent-amplified by a buffer (not shown) or the like, and thecurrent-amplified timing signals may be sequentially fed to thedownstream circuits. A large number of circuits or elements areconnected to the wiring through which the timing signals are fed, sothat the load capacitance (parasitic capacitance). The buffer isprovided to prevent the sharpness of the rise or fall of the timingsignals from being reduced by this large load capacitance.

[0081] The timing signals from the shift register 102 a are then fed tothe latch (A) 102 b. The latch (A) 102 b has a plurality of stages oflatches for processing n-bit digital video signals. The latch (A) 102 bsequentially writes in and holds the n-bit digital video signalsincluding image information upon input of the timing signals.

[0082] Note that the digital video signals may be sequentially fed tothe plural stages of the latches of the latch (A) 102 b when the digitalvideo signals are taken in by the latch (A) 102 b. However, the presentinvention is not limited to this structure. A so-called division drivemay be performed in which the plural stages of latches of the latch (A)102 b are divided into a number of groups and then the digital videosignals are parallely fed to the respective groups at the same time. Itis to be noted that the number of groups at this point is called adivision number. For example, if the latches are grouped into 4 stageseach, then it is called a 4-branch division drive.

[0083] The time necessary to complete writing of the digital videosignals into all the stages of the latches of the latch (A) 102 b iscalled a line period. In other words, the line period is defined as atime interval from the start of writing the digital video signals intothe latch of the leftmost stage to the end of writing the digital videosignals into the latch of the rightmost stage in the latch (A) 102 b. Inpractice, a line period may be a period in which a horizontal returnperiod is added to the above line period.

[0084] After the completion of one line period, a latch signal is fed tothe latch (B) 102 c. At this moment, the digital video signals writtenin and held by the latch (A) 102 b are sent all at once to the latch (B)102 c to be written in and held by all the stages of latches thereof.

[0085] Sequential writing-in of digital video signals on the basis ofthe timing signals from the shift register 102 a is again carried out tothe latch (A) 102 b after it has completed sending the digital videosignals to the latch (B) 102 c.

[0086] During this second time one line period, the digital videosignals written in and held by the latch (B) 102 b are inputted tosource signal lines.

[0087] On the other hand, the gate signal line driver circuit 103 iscomposed of a shift register and a buffer (both not shown in thefigure). Depending on the situation, the gate signal line driver circuit103 may have a level shifter beside the shift register and the buffer.

[0088] In the gate signal line driver circuit 103, the timing signalsfrom the shift register (not shown in the figure) are fed to the buffer(not shown in the figure) to be fed to corresponding gate signal lines(also referred to as scanning lines). The gate signal lines areconnected to the gate electrodes of the switching TFTs of one line, andall the switching TFTs of one line have to be turned ON simultaneously.Therefore, the use of a buffer with a large electric current capacity isrequired.

[0089] It is to be noted that the structure, the driving method, and thenumber of the source signal line driver circuit 102 and the gate signalline driver circuit 103 are not limited to the structure in theembodiment mode.

[0090] Shown in FIG. 5 is a timing chart illustrating a case where theEL display of the present invention is driven by the digital method toperform a display.

[0091] First, a 1 frame period (F) is divided into an “n” number ofsub-frame periods (SF1 to SFn). Note that a period in which all thepixels in the pixel portion display 1 image is referred to as the 1frame period (F).

[0092] The provision of 60 or more frame periods within one second bythe EL display is preferred. The glimmering of images such as flickeringmay be visually suppressed by providing the number of images displayedin one second to be 60 or more.

[0093] Note that a period in which 1 frame period is divided into aplurality of periods is referred to as sub-frame period (SF). As thenumber of tones increase, the number of sub-frame periods in 1 frameperiod also increases.

[0094] The subframe periods are divided into address periods (Ta) andsustain periods (Ts). The address period is a period required forinputting digital video signals into all of the pixels during onesubframe period, and the sustain period (also referred to as a turn onperiod) denotes a period in which the EL element is made to either emitlight or not to thereby perform display by the digital video signalsinputted to the pixels in the address period.

[0095] The address periods (Ta) of SF1 to SFn are Ta1 to Tan,respectively. The sustain periods (Ts) of SF1 to SFn are Ts1 to Tsn,respectively.

[0096] The electric potential of the power source supply lines (V1 toVx) is maintained at a predetermined electric potential (power sourceelectric potential).

[0097] First, in the address period Ta, the electric potential of theopposing electrodes of both the display EL element 142 and the sensor ELelement 132 is maintained at a level equivalent to the power sourceelectric potential.

[0098] Then, a gate signal is fed to the gate signal line G1. Among theplural number of switching TFTs 140 of the display pixels 105 and theplural number of switching TFTs 130 of the sensor pixels 104, all theswitching TFTs connected to the gate signal line G1 are turned into theON state. Note that throughout this specification. a TFT in the ON stateis referred to as driving of a TFT.

[0099] Next, the digital video signals from the source signal linedriver circuit 102 are fed to the source signal lines (S1 to Sx) in thestate that all the switching TFTs connected to the gate signal line G1are turned into the ON state. The digital video signals have theinformation [0] or [1]. The digital video signals [0] and [1] aresignals where one has a “Hi” (High) voltage while the other has an “Lo”(Low) voltage.

[0100] Then via the switching TFTs that are in the ON state, the digitalvideo signals that are fed to the source signal lines (S1 to Sx) are fedto the gate electrode of the EL driving TFT, which is connected to thesource region or the drain region of the switching TFTs.

[0101] Next, the gate signal is fed to the gate signal line G2, wherebyall the switching TFTs 1501 that are connected to the gate signal lineG2 turn into the ON state. Among the plural number of switching TFTs 140of the display pixels 105 and the plural number of switching TFTs 130 ofthe sensor pixels 104, all the switching TFTs connected to the gatesignal line G2 are turned into the ON state.

[0102] The digital video signals from the source signal line drivercircuit 102 are then fed to the source signal lines (S1 to Sx) in thestate that all the switching TFTs connected to the gate signal line G2are turned into the ON state. Then via the switching TFTs that are inthe ON state, the digital video signals that are fed to the sourcesignal lines (S1 to Sx) are fed to the gate electrode of the EL drivingTFT, which is connected to the source region or the drain region of theswitching TFTs.

[0103] The above-described operation is repeated until the gate signalis fed to the gate signal line Gy to thereby input the digital videosignals to all the display pixels 105 and the sensor pixels 104. Aperiod until the completion of inputting the digital video signals toall the display pixels 105 and the sensor pixels 104 is the addressperiod. Note that the lengths of the respective address periods (Ta1 toTan) of the “n” number of sub-frame periods are all the same.

[0104] Upon the completion of the address period Ta, a sustain periodbegins. In the sustain period, the electric potential of all theopposing electrodes of the EL elements is set to a level where it has anelectric potential difference with the power source electric potentialto the extent that the EL element emits light when the power sourceelectric potential is applied to the pixel electrode.

[0105] Thereafter, in the sustain period, all the switching TFTs of thedisplay pixels 105 and the sensor pixels 104 are turned into the OFFstate. The digital video signal fed to the display pixels 105 and thesensor pixels 104 is then fed to the gate electrode of the EL drivingTFT of each of the pixels.

[0106] In the embodiment mode, when the digital video signal has theinformation [0], then the EL driving TFT is turned into the OFF state.Therefore, the pixel electrode of the EL element is in the state ofbeing maintained at the electric potential of the opposing electrode. Asa result, the EL element of the pixel to which the digital video signalhaving the information [0] is inputted does not emit light.

[0107] On the other hand, when the digital video signal has theinformation [1], then the EL driving TFT is turned into the ON state inthe embodiment mode. Therefore, the power source electric potential isapplied to the pixel electrode of the EL element. As a result, the ELelement of the pixel to which the digital video signal having theinformation [1] is inputted emits light.

[0108] Thus, the EL element either emits light or not depending on theinformation of the digital video signal to the pixels, whereby thepixels perform display.

[0109] Upon completion of the sustain period, 1 subframe period ends.Then the next subframe period appears and turns into an address periodagain. At the point the digital video signals have been fed to all thepixels, a sustain period begins again. It is to be noted that the orderof appearance of the sub-frame periods is arbitrary.

[0110] The same operation is repeated in the rest of the sub-frameperiods to thereby perform display. Upon the completion of the “n”number of sub-frame periods, 1 frame period ends.

[0111] Further, in the present invention, a ratio of the lengths of the“n” number of sustain periods Ts1, . . . , Tsn is expressed as Ts1: Ts2:Ts3: . . . Ts(n−1): Tsn=2⁰: 2⁻¹: 2⁻² : . . . : 2^(31(n−2)): 2^(−(n−1)).

[0112] The gradation of each pixel is determined by which subframeperiod is selected for light emission during one frame period. Forexample, if n=8, and the luminance of pixels having light emitted duringall of the sustain periods is taken as 100%, then in case of the pixelsemitting light in Ts1 and Ts2, the luminance is expressed as 70%, andwhen Ts3, Ts5, and Ts8 are selected, the luminance can be expressed as16%.

[0113] Note that in the embodiment mode, the EL element did not emitlight because the electric potential of the opposing electrode wasmaintained at an electric potential that is equivalent to the powersource electric potential in the address period. However, the presentinvention is not limited to this structure. An electric potentialdifference to the extent that EL element emit light when the powersource electric potential is applied to the pixel electrode isconstantly provided between the opposing electric potential and thepower source electric potential. Thus, the address period, similarly tothe display period, may also perform display. However, in this case, allthe subframe periods actually become periods performing display, andtherefore, the lengths of the subframe periods are set at SF1: SF2: SF3:. . . : SF(n−1): SFn=2⁰: 2⁻¹: 2⁻²: . . . : 2^(−(n−2)): 2 ⁻(n−1). Byadopting the above structure, a high luminance image can be attainedcompared with the driving method where the address periods do not emitlight.

[0114] As explained above, simultaneously with the display of an imagein the display portion depending on the luminescent or non-luminescentstate of the display EL elements, similar to the display EL elements,the sensor EL elements become either luminescent or non-luminescentstate.

[0115] Next, an explanation will be made on the mechanism of the lightreceiving diode 136 detecting the luminance of the sensor EL element 132in the sensor portion 106.

[0116] It is desirable that one of the reset TFT 134 and the buffer TFT135 of the sensor pixel 104 is an n-channel TFT, and the remaining oneis a p-channel TFT.

[0117] First, the reset TFT 134 is turned into the ON state depending ona reset signal that is fed to the rest signal line RL. Therefore, thestandard electric potential of the sensor power source line VB isapplied to gate electrode of the buffer TFT 135. The source region ofthe buffer TFT 135 is connected to the constant-current power source viathe sensor output wiring FL, whereby the electric potential differenceV_(GS) of the gate electrode and the source region of the buffer TFT 135is constantly at a fixed value. Accordingly, the source region of thebuffer TFT 135 is held at an electric potential where V_(GS) issubtracted from the standard electric potential. Note that in thisspecification, a period in which the reset TFT 134 is in the ON state isreferred to as a reset period.

[0118] Next, the electric potential of the reset signal that is fed tothe reset signal line RL is changed, whereby the reset TFT 134 is turnedinto the OFF state. Therefore, the standard electric potential of thesensor power source line VB is not applied to the gate electrode of thebuffer TFT 135. Note that a period in which the reset TFT 134 is in theOFF state is referred to as a sample period in this specification.

[0119] In case of the EL display being driven by the digital method, thesample period is longer than the address period Ta and overlaps thesustain period Ts in which the sensor EL element 132 is emitting light.

[0120] The irradiation of the light generated from the sensor EL element132 to the light receiving diode 136 makes a current flow in the lightreceiving diode 136. Therefore, the fixed electric potential of the gateelectrode of the buffer TFT 135 in the reset period changes in thesample period. The amount of the change in the electric potential willalternates on the basis of the size of the current flowing in the lightreceiving diode 136.

[0121] The current flowing in the light receiving diode 136 isproportional to the strength of the light irradiated thereto. In otherwords, compared with when the luminance of the sensor EL element 132 ishigh and when the luminance thereof is low, a larger current flows tothe light receiving diode 136 when the luminance thereof is high.Consequently, the electric potential of the gate electrode of the bufferTFT 135 undergoes a large change when the luminance 6f the sensor ELelement 132 is high compared with when the luminance thereof is low.

[0122] Because the electric potential difference V_(GS) of the sourceregion and the gate electrode of the buffer TFT 135 is always a fixedvalue, the electric potential of the source region of the buffer TFT 135is maintained at an electric potential in which V_(GS) is subtractedfrom the electric potential of the gate electrode thereof. Thus, whenthe electric potential of the gate electrode of the buffer TFT 135changes, the electric potential of the source region of the buffer TFT135 changes together therewith.

[0123] The electric potential of the source region of the buffer TFT 135is applied to the sensor output wiring FL to thereby be fed to acorrection circuit as a sensor output signal.

[0124] Shown in FIG. 6 is the block diagram of a correction circuit 201.The correction circuit 201 may be provided on the same substrate withthe display portion 101 or the sensor portion 106. Further, it may beprovided on an IC chip and be connected to the sensor portion 106 by anFPC or the like.

[0125] The correction circuit 201 is composed of an A/D convertercircuit 202, a arithmetic circuit 203, a correction memory 204, and aD/A converter circuit 205. Note that although the structure of FIG. 6shows a case where the correction memory 204 is constructed as a part ofthe arithmetic circuit 203, the correction memory 204 and the arithmeticcircuit 203 may be provided separately.

[0126] The sensor output signal from the sensor output wiring FL is fedto the A/D converter circuit 202 to thereby be converted into a digitalsensor output signal and be outputted therefrom. The digital sensoroutput signal outputted from the A/D converter circuit 202 is then fedto the arithmetic circuit 203.

[0127] When the sensor EL element 132 has an ideal luminance, the dataof the digital sensor output signal (correction standard data) that isto be fed to the arithmetic circuit 203 is stored in the correctionmemory 204.

[0128] The arithmetic circuit 203 compares the digital sensor outputsignal that was actually fed to the arithmetic circuit 203 with thecorrection standard data stored in the correction memory 204. Then thearithmetic circuit 203 calculates, from the difference between theactual sensor output signal and the correction standard data that werecompared, the level of the electric potential (power source electricpotential) of the power source supply line V necessary for the displayEL element 142 and the sensor El element 132 to obtain an idealluminance. Thereafter, the arithmetic circuit 203 feeds the digitalcorrection signal having the information of the level of the powersource electric potential to the D/A converter circuit 205.

[0129] The digital correction signal that is fed to the D/A convertercircuit 205 is converted into an analog signal to thereby be fed to anEL power source 206. The EL power source 206 applies an electricpotential whose level is determined by the inputted analog correctionsignal to the power source supply lines (V1 to Vx). In case theluminance of the EL element is reduced, the correction mechanism worksby regulating the power source electric potential of the power sourcesupply lines so as to supplement the reduction thereof to therebyenhance the luminance of the EL element.

[0130] Note that when the EL display employs the three kinds of ELelements corresponding to the colors RGB, it is necessary to provide thecorrection circuit 201 and the EL power source 206 to each of the colorsto be revised. In other words, in case of revising each of the colorsRGB, the provision of 3 correction circuits 201 and 3 EL power sources206 is necessary.

[0131] Furthermore, when the EL display employs an EL element emitting asingle color such as white, blue, or blue-green, the provision of thecorrection circuit 201 and the EL power source 206 may be one of each,or the provision thereof may be for each color to be revised. Thedeterioration rate of the EL layer differs depending on the wavelengthof the light irradiated thereto. Therefore, in case of the EL displayemploying the EL element emitting white light and a color filter, byproviding the correction circuit 201 and the EL power source 206 to eachof the colors to be revised, a more accurate correction can be made tothe luminance of the EL element corresponding to each of the colors. Asa result, a clearer image of a desirable color as well can be displayed.

[0132] In the present invention, by adopting the above structure, thedisplay EL element 142 and the sensor EL element 132 are capable ofhaving an ideal luminance, thereby making it possible for the EL displayto perform a clear and desirable color display even if the EL layer inthe EL display deteriorates.

[0133] Note that although the sensor portion has one of the sensorpixels corresponding to the respective colors RGB in the embodimentmode, the present invention is not limited thereto. A plurality ofsensor pixels corresponding to each of the colors may be provided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0134] Embodiments of the present invention are explained below.

[0135] Embodiment 1

[0136] An EL display of the present invention driven by an analog methodis explained in Embodiment 1 using FIGS. 7 to 9.

[0137] Shown in FIG. 7 is a top view of an EL display, which is aportion of a semiconductor display device of the present invention. InEmbodiment 1, an explanation will be made on an EL display forperforming color display. However, the EL display of the presentinvention not only performs color display but may also performmonochrome display.

[0138] As shown in FIG. 7, there is provided a display portion 301, asource signal line driver circuit 302, a gate signal line driver circuit303, and a sensor portion 306. The source signal line driver circuit 302is composed of a shift register 302 a, a level shifter 302 b, and asampling circuit 302 c.

[0139] The sensor portion 306 has sensor pixels 304 (R sensor pixel 304a. G sensor pixel 304 b, and B sensor pixel 304 c) that correspond tothe colors RGB, respectively. Note that an EL display of a color displaysystem that employs three kinds of EL elements corresponding to thecolors RGB is illustrated in Embodiment 1. However, Embodiment 1 is notlimited thereto, and an EL display of a color display system thatemploys an EL element emitting white light may be used. Further,although the sensor portion 306 shown in Embodiment 1 has 3 sensorpixels that correspond to the colors RGB, respectively, the presentinvention is not limited thereto. Only sensor pixels that correspond to1 or 2 colors of the colors RGB may be provided in the sensor portion.

[0140] The detailed structure of the display portion 301 and the sensorportion 306 is the same as for a case of driving by a digital method,and therefore, FIG. 2 is referenced. Note that the display portion 301,the sensor portion 306, the R sensor pixel 304 a, the G sensor pixel 304b, and the B sensor pixel 304 c, all of FIG. 7, correspond to thedisplay portion 101, the sensor portion 106, the R sensor pixel 104 a,the G sensor pixel 104 b, and the B sensor pixel 104 c, respectively, ofFIG. 2.

[0141] Note that, in Embodiment 1, the sensor portion and the displayportion are formed on the same substrate, but the present invention isnot limited thereto. A structure may be such that the sensor portion andthe display portion are formed on different substrates and connected bya connector such as an FPC.

[0142] The display portion 301 includes a plurality of display pixels.Note that the display pixels in Embodiment 1 correspond to the displaypixels 105 in FIG. 2. The display pixels 105 each have any one of sourcesignal lines (S1 to Sx), any one of power source supply lines (V1 toVx), and any one of gate signal lines (G1 to Gy). There are 3 types ofdisplay pixels: a display pixel for displaying the color R; a displaypixel for displaying the color G; and a display pixel for displaying thecolor B.

[0143] A source signal line Sp (where p is an arbitrary number between 1and x), a power source supply line Vp, and a gate signal line Gq (whereq is an arbitrary number between 1 and y) are contained in anarbitrarily selected display pixel (p, q) for displaying the color R.Also, similar to the display pixel (p, q), the source signal line Sp,the power source supply line Vp, and the gate signal line Gq arecontained in the R sensor pixel 304 a.

[0144] Also, the same source signal line, power source supply line, andgate signal line that are included in an arbitrarily selected displaypixel for displaying the color G are also contained in the G sensorpixel 304 b. Further, the same source signal line, power source supplyline, and gate signal line that are contained in an arbitrarily selecteddisplay pixel for displaying the color B are also contained in the Bsensor pixel 304 c. The structures of the display pixel and the sensorpixel 304 are the same as for the case of driving by the digital methodof FIG. 3 and FIG. 4, and therefore the embodiment mode may bereferenced for an explanation of the structures.

[0145] Next, a description will be made on a driving method of an ELdisplay of Embodiment 1.

[0146]FIG. 7 is referenced. In the source signal line driver circuit302, a clock signal (CLK) and a start pulse (SP) are inputted to theshift register 302 a. The shift register 302 a sequentially generatestiming signals on the basis of the clock signal (CLK) and the startpulse (SP) to thereby sequentially feed the timing signals to downstreamcircuits.

[0147] A timing signal from the shift register 302 a has its voltageamplitude made larger in the level shifter 302 b, and is inputted to thesampling circuit 302 c. The sampling circuit 302 c, in synchronous withthe timing signal, then samples the signal having analog imageinformation (analog video signal) in accordance with an analog switch,and the sampled signal is inputted to a corresponding source signalline.

[0148] Note that the source signal line driver circuit 302 may have abuffer. A large number of circuits or elements are connected to thewiring through which the timing signals are fed, so that the loadcapacitance (parasitic capacitance) due to those circuits or elements islarge. The buffer is effective to prevent the sharpness of the rise orfall of the timing signals from being reduced due to this large loadcapacitance.

[0149] On the other hand, the gate signal line driver circuits 303 eachhave a shift register and a buffer (neither shown in the figures).Further, the gate signal line driver circuits 303 also may have levelshifter circuits other than a shift register and a buffer.

[0150] The timing signal is supplied to the buffer (not shown in thefigure) from the shift register (not shown in the figure) in the gatesignal line driver circuit 303, and is then supplied to a correspondinggate signal line (also referred to as a scanning line). The gateelectrodes of the switching TFT for one line are connected to the Datesignal line, and all of the switching TFTs for one line must be turnedON simultaneously. Therefore, a buffer capable of handling a largeelectric current flow is used.

[0151] Note that the number of the source signal line driver circuits302 and the gate signal line driver circuits 303, the circuitstructures, and the methods of driving the circuits are not limited tothe constitution shown in Embodiment 1.

[0152] Next, a timing chart for a case of driving the EL display of thepresent invention by the analog method is shown in FIG. 8. A period fromthe selection of one gate signal line in accordance with a gate signaluntil a different gate signal line is next selected is referred to asone line period (L). Further, a period from display of one image untildisplay of the next image is referred to as one frame period (F). Whenthere are y gate signal lines, there are y line periods (L1 to Ly)formed within one frame period.

[0153] First, power source supply lines (V1 to Vx) are maintained at apredetermined electric power source potential. An opposing electrode isalso maintained at a predetermined electric potential. The electricpotential of the opposing electrode has an electric potential differencewith the electric power source potential to the extent that an ELelement emits light when the electric power source potential is appliedto a pixel electrode.

[0154] A selection signal is inputted to a gate signal line G1 in thefirst line period L1 from the gate signal line driver circuit 303. Thesampled analog video signal is then inputted to source signal lines (S1to Sx). All of the switching TFTs connected to the gate signal line G1is turned ON in accordance with the selection signal, and therefore, theanalog video signal inputted to the source signal lines is inputted tothe gate electrodes of the EL driving TFTs through the switching TFTs.

[0155] The amount of electric current flowing in a channel formingregion of the EL driving TFT is controlled by the height (voltage) ofthe electric potential of the signal inputted to its gate electrode. Theheight of the electric potential of the pixel electrode of the ELelement is therefore determined by the electric potential of the analogsignal inputted to the gate electrode of the EL driving TFT. The ELelement is then controlled by the electric potential of the analog videosignal and emits light.

[0156] The above-stated operations are repeated, and when the analogvideo signal is inputted to the source signal lines (S1 to Sx), thefirst line period L1 ends. Note that the period until completion ofanalog video signal inputted to the source signal lines (S1 to Sx) mayalso be taken together with a horizontal return period as one lineperiod. The second line period L2 then begins, and the selection signalis inputted to the gate signal line G2. Then, similar to the first lineperiod L1, the analog video signal is inputted to the source signallines (S1 to Sx) in order.

[0157] When the selection signal is inputted to all of the gate signallines (G1 to Gy), all of the line periods (L1 to Ly) are completed. Oneframe period is complete when all of the line periods (L1 to Ly) arecomplete. Display is performed in all of the pixels within one frameperiod, and one image is formed. Note that all of the line periods (L1to Ly) may be taken together with a vertical return period as one frameperiod.

[0158] The luminance of the EL elements is thus controlled in accordancewith the electric potential of the analog video signal inputted to thesource signal lines, as above. Gray-scale display is performed inaccordance with the control of luminance.

[0159] An explanation of how the luminance of display EL elements andthe luminance of sensor EL elements are corrected in accordance with asensor output signal outputted from the sensor portion 306 is explainednext using FIG. 9. Note that a light receiving diode detects theluminance of the sensor EL elements in the sensor pixel shown in FIG. 7.The processes until the sensor output signal is inputted to a sensoroutput wiring is the same as for the case of the digital drive ELdisplay shown in the embodiment mode, and therefore, the explanation isomitted.

[0160] The sensor output signal having luminance information of thesensor EL element detected by the light receiving diode is inputted to avideo signal correction circuit through a sensor output wiring FL in asampling period.

[0161] A block diagram of a video signal correction circuit 401 is shownin FIG. 9. The video signal correction circuit 401 may be formed on thesame substrate as the display portion 301 and the sensor portion 306,and it may also be formed on an IC chip and connected to the sensorportion 306 by an FPC or the like.

[0162] The video signal correction circuit 401 has an A/D convertercircuit 402, an arithmetic circuit 403, a correction memory 404, and aD/A converter circuit 405. Note that a structure for a case in which thecorrection memory 404 is a portion of the arithmetic circuit 403 isshown in FIG. 9, but the correction memory 404 and the arithmeticcircuit 403 may also be formed separately.

[0163] A signal generator 406 generates a signal having digital imageinformation (digital video signal), and this is inputted to thearithmetic circuit 403. Note that when the signal having imageinformation and output from the signal generator 406 (video signal) isanalog, the signal is first converted to a digital video signal by theA/D converter circuit and then is inputted to the arithmetic circuit403.

[0164] The sensor output signal is inputted to the A/D converter circuit402 from the sensor output wiring FL, is converted into a digital sensoroutput signal, and is then outputted. The digital sensor output signaloutputted from the A/D converter circuit 402 is then inputted to thearithmetic circuit 403.

[0165] When the display EL elements and the sensor EL elements haveideal luminances, the digital sensor output signal data inputted to thearithmetic circuit 403 (correction standard date) is stored in thecorrection memory 404.

[0166] The arithmetic circuit 403 compares the actual digital sensoroutput signal inputted to the arithmetic circuit 403 with the correctionstandard data stored in the correction memory 404. Then, based upon thecomparative difference between the actual sensor output signal and thecorrection standard data, the digital video signal inputted to thearithmetic circuit 403 from the signal generator 406 is corrected. Notethat it is very important that the digital video signal after correctionat this time has the necessary electric potential in order to obtainideal luminance levels in the display EL elements and the sensor ELelements when converted to analog.

[0167] Note that a sensor output signal corresponding to each displaycolor is inputted to the arithmetic circuit 403. For example, the threesensor output signals outputted from the R sensor pixel 304 a, the Gsensor pixel 304 b, and the B sensor pixel 304 c are inputted to thearithmetic circuit 403 in Embodiment 1. The digital video signal iscorrected such that an analog video signal having a desired heightelectric potential is sampled and inputted to pixels corresponding toeach color (the display pixels and the sensor pixels).

[0168] The corrected digital video signal is next inputted to the D/Aconverter circuit 405 from the arithmetic circuit 403. The correcteddigital video signal inputted to the D/A converter circuit 405 isconverted to analog, and is then inputted to the sampling circuit 302 cof the source signal line driver circuit 302 as an analog video signal.The analog video signal has a necessary electric potential in order toobtain the ideal luminance in the display EL elements and the sensor ELelements.

[0169] According to the above structure, in the present invention, thedisplay EL elements and the sensor EL elements can have idealluminances, even if the EL layer in the EL display deteriorates, and itbecomes possible to perform the desired color display with clarity.

[0170] Note that the sensor portion has one each of sensor pixelscorresponding to R, G, and B in Embodiment 1, but the present inventionis not limited to this. A plurality of sensor pixels corresponding toeach color may also exist.

[0171] Further, by correcting the electric potential of the analog videosignal inputted to the display portion in the video signal correctioncircuit, the luminance of the EL elements is corrected with the analogdrive EL display of Embodiment 1. However, the present invention is notlimited to this. In addition to correcting the electric potential of theanalog video signal in the video signal correction circuit, a correctioncircuit for correcting the electric power source potential may also beadded, similar to the digital drive EL display.

[0172] Embodiment 2

[0173] A method of manufacturing an EL display which uses the presentinvention is explained using FIGS. 10A to 13B. A method of manufacturinga TFT of a sensor portion is explained here, but it is also possible tosimilarly manufacture a TFT of a display portion.

[0174] First, as shown in FIG. 10A, a base film 501 is formed to athickness of 300 nm on a glass substrate 500. A silicon oxynitride filmis laminated as the base film 501 in Embodiment 2. At this point, it isappropriate to set the nitrogen concentration to between 10 and 25 wt %in the film contacting the glass substrate 500. In addition, it iseffective that the base film 501 has a thermal radiation effect, and aDLC (diamond-like carbon) film may also be provided.

[0175] Next, an amorphous silicon film (not shown in the figure) isformed with a thickness of 50 nm on the base film 501 by a knowndeposition method. Note that it is not necessary to limit to theamorphous silicon film, and another film may be formed provided that itis a semiconductor film containing an amorphous structure (including amicrocrystalline semiconductor film). In addition, a compoundsemiconductor film containing an amorphous structure, such as anamorphous silicon germanium film, may also be used. Further, the filmthickness may be made from 20 to 100 nm.

[0176] The amorphous silicon film is then crystallized by a knowntechnique, forming a crystalline silicon film (also referred to as apolycrystalline silicon film or a polysilicon film) 502. Thermalcrystallization using an electric furnace, laser annealingcrystallization using a laser light, and lamp annealing crystallizationusing an infrared lamp exist as known crystallization methods.Crystallization is performed in Embodiment 2 using an excimer laserlight, which uses XeCl gas.

[0177] Note that pulse emission excimer laser light formed into a linearshape is used in Embodiment 2, but a rectangular shape may also be used.Continuous emission argon laser light and continuous emission excimerlaser light can also be used.

[0178] In this embodiment, although the crystalline silicon film is usedas the active layer of the TFT, it is also possible to use an amorphoussilicon film as the active layer.

[0179] Note that it is effective to form the active layer of theswitching TFT, in which there is a necessity to reduce the off current,by an amorphous silicon film, and to form the active layer of an ELdriving TFT by a crystalline silicon film. Electric current flows withdifficulty in the amorphous silicon film because the carrier mobility islow, and the off current does not easily flow. In other words, the mostcan be made of the advantages of both the amorphous silicon film,through which current does not flow easily, and the crystalline siliconfilm, through which current easily flows.

[0180] Next, as shown in FIG. 10B, a protective film 503 is formed onthe crystalline silicon film 502 with a silicon oxide film having athickness of 130 nm. This thickness may be chosen within the range of100 to 200 nm (preferably between 130 and 170 nm). Furthermore, otherfilms may also be used providing that they are insulating filmscontaining silicon. The protective film 503 is formed so that thecrystalline silicon film is not directly exposed to plasma duringaddition of an impurity, and so that it is possible to have delicateconcentration control of the impurity.

[0181] Resist masks 504 a and 504 b are then formed on the protectivefilm 503, and an impurity element, which imparts n-type conductivity(hereafter referred to as an n-type impurity element), is added throughthe protective film 503. Note that elements residing in periodic tablegroup 15 are generally used as the n-type impurity element, andtypically phosphorous or arsenic can be used. Note that a plasma dopingmethod is used, in which phosphine (PH₃) is plasma-activated withoutseparation of mass, and phosphorous is added at a concentration of1×10¹⁸ atoms/cm³ in Embodiment 2. An ion implantation method, in whichseparation of mass is performed, may also be used, of course.

[0182] The dose amount is regulated such that the n-type impurityelement is contained in an n-type impurity region (b) 505, thus formedby this process, at a concentration of 2×10¹⁶ to 5×10¹⁹ atoms/cm³(typically between 5×10¹⁷ and 5×10¹⁸ atoms/cm³).

[0183] Next, as shown in FIG. 10C, the protective film 503 and theresist masks 504 a and 504 b are removed, and an activation of the addedn-type impurity elements is performed. A known technique of activationmay be used as the means of activation, but activation is done inEmbodiment 2by irradiation of excimer laser light (laser annealing). Ofcourse, a pulse emission excimer laser and a continuous emission excimerlaser may both, be used, and it is not necessary to place any limits onthe use of excimer laser light. The goal is the activation of the addedimpurity element, and it is preferable that irradiation is performed atan energy level at which the crystalline silicon film does not melt.Note that the laser irradiation may also be performed with theprotective film 503 in place.

[0184] The activation by heat treatment (furnace annealing) may also beperformed along with activation of the impurity element by laser light.When activation is performed by heat treatment, considering the heatresistance of the substrate, it is good to perform heat treatment at onthe order of 450 to 550° C.

[0185] A boundary portion (connecting portion) with end portions of then-type impurity region (b) 505, namely regions, in which the n-typeimpurity element is not added, on the periphery of the n-type impurityregion (b) 505, is delineated by this process. This means that, at thepoint when the TFTs are later completed, extremely good connectingportion can be formed between LDD regions and channel forming regions.

[0186] Unnecessary portions of the crystalline silicon film are removednext, as shown in FIG. 10D, and island-shape semiconductor films(hereafter referred to as active layers) 506 to 509 are formed.

[0187] Then, as shown in FIG. 10E, a gate insulating film 510 is formed,covering the active layers 506 to 509. An insulating film containingsilicon and with a thickness of 10 to 200 nm, preferably between 50 and150 nm, may be used as the gate insulating film 510. A single layerstructure or a lamination structure may be used. A 110 nm thick siliconoxynitride film is used in Embodiment 2.

[0188] Thereafter, a conductive film having a thickness of 200 to 400 nmis formed and patterned to form gate electrodes 511 to 515. InEmbodiment 2, the gate electrodes and wirings (hereinafter referred toas gate wirings) electrically connected to the gate electrodes forproviding conductive paths are formed of different materials from eachother. More specifically, the gate wirings are made of a material havinga lower resistivity than the gate electrodes. This is because a materialenabling fine processing is used for the gate electrodes, while the gatewirings are formed of a material that can provide a smaller wiringresistance but is not suitable for fine processing. It is of coursepossible to form the gate electrodes and the gate wirings with the samematerial.

[0189] Although the gate electrode can be made of a single-layeredconductive film, it is preferable to form a lamination film with morethan two layers for the gate electrode if necessary. Any knownconductive films can be used for the gate electrode. It should be noted,that it is preferable to use such a material that enables fineprocessing, and more specifically, a material that can be patterned witha line width of 2 μm or less.

[0190] Typically, it is possible to use a film made of an elementselected from the group consisting of tantalum (Ta), titanium (Ti),molybdenum (Mo), tungsten (W), chromium (Cr), and silicon (Si), a filmof nitride of the above element (typically a tantalum nitride film,tungsten nitride film, or titanium nitride film), an alloy film ofcombination of the above elements (typically Mo-W alloy or Mo-Ta alloy),or a silicide film of the above element (typically a tungsten silicidefilm or titanium silicide film). Of course, the films may be used as asingle layer or a laminate layer.

[0191] In Embodiment 2, a laminate film of a tungsten nitride (WN) filmhaving a thickness of 30 nm and a tungsten (W) film having a thicknessof 370 nm is used. This may be formed by sputtering. When an inert gassuch as Xe or Ne is added as a sputtering gas, film peeling due tostress can be prevented.

[0192] The gate electrode 511 is formed at this time so as to overlap aportion of the n-type impurity region (b) 505. This overlapping portionlater becomes an LDD region overlapping the gate electrode (FIG. 10E).

[0193] Next, an n-type impurity element (phosphorous is used inEmbodiment 2) is added in a self-aligning manner with the gateelectrodes 511 to 515 as masks, as shown in FIG. 11A. The addition isregulated such that phosphorous is added to n-type impurity regions (c)516 to 523 thus formed at a concentration of{fraction (1/10)} to ½ thatof the n-type impurity region (b) 505 (typically between ¼ and ⅓).Specifically, a concentration of 1×10¹⁶ to 5×10¹⁸ atoms/cm³ (typically3×10¹⁷ to 3×10¹⁸ atoms/cm³ ) is preferable.

[0194] Resist masks 524 a to 524 c are formed next, with a shapecovering the gate electrodes 512 to 515 and the like, as shown in FIG.11B, and an n-type impurity element (phosphorous is used in Embodiment2) is added, forming impurity regions (a) 525 to 529 containingphosphorous at high concentration. Ion doping using phosphine (PH₃) isalso performed here, and the phosphorous concentration of these regionsis regulated so as to be set to from 1×10²⁰ to 1×10²¹ atoms/cm³(typically between 2×10²⁰ and 5×10² atoms/cm³).

[0195] A source region or a drain region of the n-channel TFT is formedby this process, and in a switching TFT, a portion of the n-typeimpurity regions (c) 519 to 521 formed by the process of FIG. 11A isremained. These remaining regions correspond to LDD regions of theswitching TFT.

[0196] Next, as shown in FIG. 11C, the resist masks 524 a to 524 d areremoved, and new resist masks 530 a and 530 b are formed. A p-typeimpurity element (boron is used in Embodiment 2) is then added, formingp-type impurity regions 531 to 534 containing boron at highconcentration. Boron is added here to form the p-type impurity regions531 to 534 at a concentration of 3×10²⁰ to 3×10^(2l) atoms/cm³(typically between 5×10²⁰ and 1×10²¹ atoms/cm³) by ion doping usingdiborane (B₂H₆).

[0197] Note that phosphorous has already been added to the p-typeimpurity regions 531 to 534 at a concentration of 1×10²⁰ to 1×10²¹atoms/cm³, but boron is added here at a concentration of at least 3times that of the phosphorous. Therefore, the n-type impurity regionsalready formed completely invert to p-type, and function as p-typeimpurity regions.

[0198] Next, after removing the resist masks 530 a and 530 b, the n-typeor p-type impurity elements added to the active layer at respectiveconcentrations are activated. Furnace annealing, laser annealing or lampannealing can be used as a means of activation. In Embodiment 2, heattreatment is performed for 4 hours at 550° C. in a nitrogen atmospherein an electric furnace.

[0199] At this time, it is critical to eliminate oxygen from thesurrounding atmosphere as much as possible. This is because when evenonly a small amount of oxygen exists, an exposed surface of the gateelectrode is oxidized, which results in an increased resistance andlater makes it difficult to form an ohmic contact with the gateelectrode. Accordingly, the oxygen concentration in the surroundingatmosphere for the activation process is set at 1 ppm or less,preferably at 0.1 ppm or less.

[0200] After the activation process is completed, a gate wiring (gatesignal line) 535 having a thickness of 300 nm is formed. As a materialfor the gate wiring 535, a metal film containing aluminum (Al) or copper(Cu) as its main component (occupied 50 to 100% in the composition) canbe used. The gate wiring 335 is arranged so as to provide electricalconnection for the gate electrodes 513 and 514 of the switching TFT (seeFIG. 11D).

[0201] The above-described structure can allow the wiring resistance ofthe gate wiring to be significantly reduced, and therefore, an imagedisplay region (display portion) with a large area can be formed. Morespecifically, the pixel structure in accordance with Embodiment 2isadvantageous for realizing an EL display device having a display screenwith a diagonal size of 10 inches or larger (or 30 inches or larger.) Afirst interlayer insulating film 537 is formed next, as shown in FIG.12A. A single layer insulating film containing silicon is used as thefirst interlayer insulating film 537, or a lamination film may be used.Further, a film thickness of between 400 nm and 1.5 μm may be used. Alamination structure of an 800 nm thick silicon oxide film on a 200 nmthick silicon oxynitride film is used in Embodiment 2.

[0202] In addition, heat treatment is performed for 1 to 12 hours at 300to 450° C. in an atmosphere containing between 3 and 100% hydrogen,performing hydrogenation. This process is one of hydrogen termination ofdangling bonds in the semiconductor film by hydrogen, which is thermallyactivated. Plasma hydrogenation (using hydrogen activated by plasma) mayalso be performed as another means of hydrogenation.

[0203] Note that the hydrogenation processing may also be insertedduring the formation of the first interlayer insulating film 537.Namely, hydrogen processing may be performed as above after forming the200 nm thick silicon oxynitride film, and then the remaining 800 nmthick silicon oxide film may be formed.

[0204] Next, a contact hole is formed in the first interlayer insulatingfilm 537, and source wirings 538 to 541 and drain wirings 542 to 545 areformed. In this embodiment, this electrode is made of a laminate film ofthree-layer structure in which a titanium film having a thickness of 100nm, an aluminum film containing titanium and having a thickness of 300nm, and a titanium film having a thickness of 150 nm are continuouslyformed by sputtering. Of course, other conductive films may be used.

[0205] A first passivation film 547 is formed next with a thickness of50 to 500 nm (typically between 200 and 300 nm) as shown in FIG. 12B. A300 nm thick silicon oxide nitride film is used as the first passivationfilm 547 in Embodiment 2. This may also be substituted by a siliconnitride film. Note that it is effective to perform plasma processingusing a gas containing hydrogen such as H₂ or NH₃ before the formationof the silicon oxynitride film. Hydrogen activated by this preprocess issupplied to the first interlayer insulating film 537, and the filmquality of the first passivation film 547 is improved by performing heattreatment. At the same time, the hydrogen added to the first interlayerinsulating film 537 diffuses to the lower side, and the active layerscan be hydrogenated effectively.

[0206] Next, a second interlayer insulating film 548 made of organicresin is formed. As the organic resin, it is possible to use polyimide,polyamide, acryl, BCB (benzocyclobutene) or the like. Especially, sincethe second interlayer insulating film 548 is primarily used forleveling, acryl excellent in leveling properties is preferable. In thisembodiment, an acrylic film is formed to a thickness sufficient to levela stepped portion formed by TFTs. It is appropriate that the thicknessis made 1 to 5 μm (more preferably, 2 to 4 μm) (FIG. 12B).

[0207] Next, a contact hole is formed in the second interlayerinsulating film 548 and the first passivation film 547 so as to reachthe drain wiring 543, and a cathode electrode 549 of a light receivingdiode (photoelectric converting element) is formed so as to contact thedrain wiring 543. Aluminum formed by sputtering is used in this metallicfilm in Embodiment 2, but other metals, for example titanium, tantalum,tungsten, and copper can also be used. Further, a lamination film madefrom titanium, aluminum, and titanium may also be used.

[0208] Patterning is next performed after depositing an amorphoussilicon film containing hydrogen over the entire surface of thesubstrate, and a photoelectric converting layer 550 is formed. Atransparent conductive film is formed on the entire surface of thesubstrate next. A 200 nm thick ITO film is deposited by sputtering asthe transparent conductive film in Embodiment 2. The transparentconductive film is patterned, forming an anode electrode 551. (See FIG.12C.) A third interlayer insulating film 553 is then formed, as shown inFIG. 13A. A level surface can be obtained by using a resin such aspolyimide, polyamide, polyimide amide, or acrylic as the thirdinterlayer insulating film 553. A polyimide film having a thickness of0.7 μm is formed over the entire surface of the substrate as the thirdinterlayer insulating film 553 in Embodiment 2.

[0209] A contact hole is next formed in the third interlayer insulatingfilm 553, the second interlayer insulating film 548, and the firstpassivation film 547 so as to reach the drain wiring 545, and a pixelelectrode 555 is formed. Further, a contact hole for reaching the anodeelectrode 551 is formed in the third interlayer insulating film 553, anda sensor wiring 554 is formed. A 110 nm thick ITO (indium tin oxide)film is formed in Embodiment 2, and then patterning is performed,forming the sensor wiring 554 and the pixel electrode 555 at the sametime. Furthermore, indium oxide mixed with between 2 and 20% of zincoxide (ZnO) may also be used as the transparent conductive film. Thepixel electrode 555 becomes an EL element anode.

[0210] A bank 556 is formed next from a resin material. The bank 556 maybe formed by patterning an acrylic film or polyimide film having athickness of 1 to 2 μm. The bank 556 is formed having a stripe shapebetween pixels. The bank 556 may be formed along and on the sourcewiring 540, and it may also be formed along and on the gate wiring 535.Note that a material such as a pigment may be mixed into the resinmaterial forming the bank 661, and the bank 661 may be used as ashielding film.

[0211] An EL layer 557 and a cathode (MgAg electrode) 558 are formednext in succession without exposure to the atmosphere by using vacuumevaporation. Note that the film thickness of the EL layer 557 may befrom 80 to 200 nm (typically between 100 and 120 nm), and the thicknessof the cathode 558 may be from 180 to 300 nm (typically between 200 and250 nm). In addition, only one pixel is shown in Embodiment 2, but an ELlayer for emitting red color light, an EL layer for emitting green colorlight, and an EL layer for emitting blue color light are formedsimultaneously.

[0212] EL layers 557 are sequentially formed with respect to the pixelcorresponding to the color red, the pixel corresponding to the colorgreen, and the pixel corresponding to the color blue, respectively, bythis process. However, the EL layers 557 have little resistance tosolution, and therefore, the EL layers 557 for the respective colorsmust be formed separately without using photolithography. It is thenpreferable to cover locations other than that of the desired pixels byusing a metal mask, and then form the EL layers 557 selectively only inrequired locations.

[0213] In other words, first, a mask for covering everything except forthe pixel corresponding to the color red is set, and an EL layer whichemits red color light is selectively formed using the mask. A mask forcovering everything except for the pixel corresponding to the colorgreen is set next, and an EL layer which emits green color light isselectively formed using the mask. Finally, a mask for covering allareas outside of the pixel corresponding to the color blue is set, andan EL layer which emits blue color light is selectively formed using themask. Note that a case of using different masks is stated here, but thesame mask may also be reused. Further, it is preferable to performprocessing without releasing the vacuum until the EL layers of all ofthe pixels have been formed.

[0214] Note that the EL layer 557 is a single layer structure composedof only a light emitting layer in Embodiment 2, but the EL layer 557 mayalso have a hole transport layer, a hole injection layer, on electrontransport layer, and an electron injection layer. Various examples ofthis type of combination have already been reported upon, and any ofthese structures may be used. Known materials can be used as the ELlayer 557. It is preferable to use an organic material as the knownmaterial, considering the EL driver voltage.

[0215] The cathode 558 is formed next. An example of using an MgAgelectrode as the cathode of an EL element is shown in Embodiment 2, butit is also possible to use other known materials.

[0216] An active matrix substrate having the structure shown in FIG. 13Bis thus completed. Note that the processes after forming the bank 556and until the formation of the cathode 558 may be performed insuccession, without exposure to the atmosphere, using a multi-chambermethod (or in-line method) thin film formation apparatus.

[0217] Note also that a method of manufacturing a TFT of a sensorportion is explained in Embodiment 2, but a TFT of a display portion anda driver circuit TFT may also be formed simultaneously on the substrate.

[0218] A buffer TFT 570, which is an n-channel TFT, has a structure inEmbodiment 2in which hot carrier injection is reduced with as littledrop in operating speed as possible, as shown in FIG. 13B. An activelayer of the buffer TFT 570 contains a source region 580, a drain region581, an LDD region 582, and a channel forming region 583. The LDD region582 overlaps the gate electrode 511 through the gate insulating film510.

[0219] The formation of the LDD region on only the drain region side isin consideration of not causing the operating speed to drop. Further, itis not necessary to be too concerned with the value of the off currentfor the buffer TFT 570, and more importance may be placed on theoperating speed. It is therefore preferable for the LDD region 582 tocompletely overlap with the gate electrode 511, and to reduce resistivecomponents as much as possible. Namely, the so-called offset should beeliminated.

[0220] Furthermore, degradation due to hot carrier injection is almostof no concern for a reset TFT 571 and an EL driving TFT 573, which arep-channel TFTs, and therefore LDD regions do not have to be formed inparticular. It is also possible, of course, to form an LDD regionsimilar to that of an n-channel TFT to take action against hot carriers.

[0221] An active layer of a switching TFT 572 in Embodiment 2contains asource region 590, a drain region 591, LDD regions 592 to 595, channelforming regions 596 and 597, and a separation region 598. The LDDregions 592 to 595 are formed so as not to overlap with the gateelectrodes 513 and 514 through the gate insulating film 510. This typeof structure is extremely effective in reducing the off current.

[0222] Further, the switching TFT 572 has a double gate structure, andby using the double gate structure, this effectively becomes a structurehaving two TFTs connected in series, and has the advantage of beingcapable of reducing the value of the off current. Note that the doublegate structure is used in Embodiment 2, but a single gate structure mayalso be used, and a multiple gate structure possessing more than threegates may also be used.

[0223] Note also that, in practice, after completing through FIG. 13B,it is preferable to perform packaging (sealing) using a protective film(such as a laminate film or an ultraviolet hardened resin film), or alight transmitting sealing member, having high airtight properties andlittle outgassing, in order to have no exposure to the atmosphere. TheEL element reliability is increased if the inside of the sealing memberis filled with an inert gas atmosphere and a drying agent (barium oxide,for example) is arranged within the sealing member.

[0224] Further, after increasing airtightness by the packaging process,the device is completed as a manufactured product by attaching aconnector (flexible printed circuit, FPC) for connecting terminalspulled around from the elements or circuits formed on the substrate withexternal signal terminals. This shipping-ready state is referred to asan EL display (EL module) throughout this specification.

[0225] Note that it is possible to implement Embodiment 2in combinationwith Embodiment 1.

[0226] Embodiment 3

[0227] An example in which light emitted from an EL element isirradiated to the side of a substrate on which TFTs are formed isexplained in Embodiment 2. Using FIG. 14, an example of irradiatinglight emitted from an EL element to the opposite side of the substrateon which TFTs are formed is explained in Embodiment 3.

[0228] Although a p-channel TFT was used for the EL driving TFT inEmbodiment 2, an n-channel TFT was used for the EL driving TFT in thisembodiment. Accordingly, the active later in the EL driving TFT wascovered with a mask in a process for adding n-type impurity, and theactive layer in the EL driving TFT was not covered with the mask in theprocess for adding p-type impurity.

[0229] After forming a third interlayer insulating film 653, a contacthole for reaching a drain wiring 645 is formed in the third interlayerinsulating film 653, a second interlayer insulating film 648, and afirst passivation film 647. A pixel electrode 655 is then formed.Further, a contact hole is formed in the third interlayer insulatingfilm 653 in order to reach an anode electrode 651, and a sensor wiring654 is formed. A 300 nm thick aluminum alloy film (an aluminum filmcontaining 1 wt % of titanium) is formed in Embodiment 3, and patterningis then performed, simultaneously forming the sensor wiring 654 and thepixel electrode 655. Note that although the pixel electrode and thesensor wiring are formed using an aluminum alloy film in Embodiment 3,the present invention is not limited to this, and MgAg may also be used.Further, it is possible to use all other materials known to be used asan EL element cathode.

[0230] A bank 661 made of a resin material is formed next, as shown inFIG. 14. The bank 661 may be formed by patterning an acrylic film or apolyimide film having a thickness of 1 to 2 μm. The bank 661 is formedin a stripe shape between pixels. The bank 661 may be formed on andalong a source wiring (source signal line) 640, and may be formed on andalong a gate wiring (gate signal line) 635. Note that a material such asa pigment may be mixed into the resin material forming the bank 661, andthe bank 661 may be used as a shielding film.

[0231] A light emitting layer 656 is formed next. Specifically, anorganic EL material which becomes the light emitting layer 656 isdissolved in a solvent such as chloroform, dichloromethane, xylene,toluene, or tetrahydrobenzene, and applied. The solvent is thenvaporized by performing heat treatment, and the organic EL materiallight emitting layer is formed.

[0232] Note that only one pixel is shown in Embodiment 3, but a lightemitting layer for emitting red color light, a light emitting layer foremitting green color light, and a light emitting layer for emitting bluecolor light are formed simultaneously. In Embodiment 3,Cyano-polyphenylene vinylene is formed as the red color light emittinglayer, polyphenylene vinylene is formed as the green light emittinglayer, and polyalkylphenylene is formed as the blue light emittinglayer, each having a thickness of 50 nm. Further, 1,2-dichloromethane isused as the solvent, and heat treatment is performed by hotplate at atemperature of 80 to 150° C. for between 1 and 5 minutes, vaporizingmoisture.

[0233] A 20 nm thick hole injection layer 657 is formed next. The holeinjection layer 657 may be formed common for all pixels, and thereforeit may be formed using spin coating or printing. Polythiophene (PEDOT)in aqueous solution is applied in Embodiment 3, and then heat treatmentis performed for 1 to 5 minutes by using a hotplate at a temperaturefrom 100 to 150° C., vaporizing moisture. Polyphenylene vinylene andpolyalkylphenylene do not dissolve in water, and therefore it ispossible in this case to form the hole injection layer 657 withoutdissolution of the light emitting layer 656.

[0234] Note that it is also possible to use a low molecular weightorganic EL material as the hole injection layer 657. In that case, itmay be formed by evaporation.

[0235] A two layer structure of a light emitting layer and a holeinjection layer is taken as the EL layer in Embodiment 3, but inaddition, a hole transport layer, an electron injection layer, and anelectron transport layer may also be formed. Various examples of thistype of combination have already been reported upon, and any of thesestructures may be used.

[0236] An anode 658 is formed, as an opposing electrode, of a 120 nmthick transparent conductive film after formation of the light emittinglayer 656 and the hole injection layer 657. A transparent conductivefilm in which 10 to 20 wt % of zinc oxide is added to indium oxide isused in Embodiment 3. It is preferable to form the anode 658 byevaporation at room temperature so as not to cause degradation of thelight emitting layer 656 and the hole injection layer 657.

[0237] A fourth interlayer insulating film 659 is formed once the anode658 is formed. A level surface can be obtained by using a resin such aspolyimide, polyamide, polyimide amide, or acrylic as the fourthinterlayer insulating film 659. A 0.7 μm thick polyimide film is formedover the entire surface of the substrate as the fourth interlayerinsulating film 659 in Embodiment 3.

[0238] Next, an aluminum alloy film (an aluminum film containing 1 wt %of titanium) is formed with a thickness of 300 nm on the fourthinterlayer insulating film 659. Patterning is performed, forming areflecting plate 660. It is very important to form the reflecting plate660 in a position such that light emitted by the EL element is reflectedin the reflecting plate 660 and is made incident to a photoelectricconverting layer 650 of a light receiving diode.

[0239] Note that, although the reflecting plate 660 is formed using analuminum allow film in Embodiment 3, the present invention is notlimited to this. It is possible to use a known material provided that itis a non-transparent metal. For example, a film of an element selectedfrom the group consisting of copper (Cu), silver (Ag), tantalum (Ta),titanium (Ti), molybdenum (Mo), tungsten (W), chromium (Cr), and silicon(Si); or a nitride film of one of these elements (typically a tantalumnitride film, a tungsten nitride film, or a titanium nitride film); oran alloy film of a combination of these elements (typically an Mo-Walloy or an Mo-Ta alloy); or a silicide film of one of these elements(typically a tungsten silicide film or a titanium silicide film) can beused. A single layer structure and a lamination structure may be used,of course.

[0240] An active matrix substrate having a structure as shown in FIG. 14is thus completed. Note that reference numeral 670 denotes a buffer TFT,reference numeral 671 denotes a reset TFT, 672 denotes a switching TFT,and 673 denotes an EL driving TFT.

[0241] Note also that the process of manufacturing the TFT of the sensorportion is explained in Embodiment 3, but a TFT of a display portion anda driver circuit TFT may also be formed on the substrate at the sametime.

[0242] Further, after completing through FIG. 14, it is preferable inpractice to perform packaging (sealing) using a protective film (such asa laminate film or an ultraviolet hardened resin film), or a lighttransmitting sealing member, having high airtight properties and littleoutgassing, in order to have no exposure to the atmosphere. Thereliability of the EL elements is increased if the inside of the sealingmember is filled with an inert gas atmosphere and a drying agent (bariumoxide, for example) is arranged within the sealing member.

[0243] Further, after increasing airtightness by the packaging process,the device is completed as a manufactured product by attaching aconnector (flexible printed circuit, FPC) for connecting terminalspulled around from the elements or circuits formed on the substrate withexternal signal terminals. This shipping-ready state is referred to asan EL display (EL module) throughout this specification.

[0244] Note that it is possible to implement Embodiment 3in combinationwith Embodiment 1.

[0245] Embodiment 4

[0246] An EL display of the present invention in which the structure ofa sensor pixel differs from that of the embodiment mode and those ofEmbodiment 1 to Embodiment 3is explained in Embodiment 4.

[0247] A circuit diagram of the sensor pixel in the EL display ofEmbodiment 4 is shown in FIG. 15. A region that is surrounded by adotted line is the sensor pixel 704. Contained in the sensor pixel 704are a source signal line S (any one of the lines between (S1 and Sx)), apower source supply line V (any one of the lines between (Vi and Vx)),and a gate signal line G (any one of the lines between (G1 and Gy)).

[0248] In addition, the sensor pixel 704 has a switching TFT 730, an ELdriving TFT 731, and a sensor EL element 732. A capacitor 733 isprovided in the structure of FIG. 15, but the structure thereof may beformed without the provision of the capacitor 733.

[0249] The sensor EL element 732 is composed of an anode, a cathode, andan EL layer provided therebetween. When the anode is connected to adrain region of the EL driving TFT 731, the anode is a pixel electrode,and the cathode is an opposing electrode. On the other hand, when thecathode is connected to the drain region of the EL driving TFT 731, thecathode is the pixel electrode, and the anode is the opposing electrode.

[0250] A gate electrode of the switching TFT 730 is connected to thegate signal line G. One of a source region and a drain region of theswitching TFT 730 is connected to the source signal line S, and theother is connected to a gate electrode of the EL driving TFT 731.

[0251] One of a source region and the drain region of the EL driving TFT731 is connected to the power source supply line V, and the other isconnected to the sensor EL element 732. The capacitor 733 is provided soas connected to the gate electrode of the EL driving TFT 731 and thepower source supply line V.

[0252] Further, the sensor pixel 704 has a reset TFT 734, a buffer TFT735, and a sensor TFT 736.

[0253] It is preferable that one of the reset TFT 734 and the buffer TFT735 of the sensor pixel 704 be an n-channel TFT and that the remainingTFT be a p-channel TFT. Furthermore, it is preferable that the polarityof the buffer TFT 735 and the sensor TFT 736 be the same.

[0254] A gate electrode of the reset TFT 734 is connected to a resetsignal line RL. A source region of the reset TFT 734 is connected to asensor power source line VB and a drain region of the buffer TFT 735.The sensor power source line VB is constantly held at a fixed electricpotential (standard electric potential). Furthermore, a drain region ofthe reset TFT 734 is connected to a drain region of the sensor TFT 736and a gate electrode of the buffer TFT 735.

[0255] A source region of the buffer TFT 735 is connected to a sensoroutput wiring FL. The sensor output wiring FL is further connected to aconstant-current power source 737 and a fixed current constantly flowstherein. Further, a drain region of the buffer TFT 735 is connected tothe sensor power source line VB which is constantly maintained at afixed standard electric potential. The buffer TFT 735 functions as asource follower.

[0256] A source region of the sensor TFT 736 is maintained at apredetermined electric potential. A gate electrode of the sensor TFT 736is then connected to a sensor TFT power source line SVB and is alwaysmaintained at a fixed electric potential. The electric potentialdifference V_(GS) between the gate electrode and the source region ofthe sensor TFT is maintained such that the sensor TFT is alwaysmaintained in the OFF state. Note that the source region and the gateelectrode of the sensor TFT 736 may also have an electrically connected,structure. In this case, the electric potential difference V_(GS)between the gate electrode and the source region of the sensor TFT is 0V, and therefore the sensor TFT will always be in the OFF state.

[0257] Drive of the sensor pixel 704 is explained next.

[0258] First, the reset TFT 734 is placed in the ON state in accordancewith a reset signal inputted by the reset signal line RL. The standardelectric potential of the sensor power source line VB is thereforeapplied to the gate electrode of the buffer TFT 735. The source regionof the buffer TFT 735 is then connected to constant-current power sourcethrough the sensor output wiring FL, and the electric potentialdifference V_(GS) between the source region and the gate electrode ofthe buffer TFT 735 is always fixed. The source region of the buffer TFT735 is therefore maintained at an electric potential in which V_(GS) issubtracted from the standard electric potential. Note that a periodduring which the reset TFT 734 is in the ON state is referred to as areset period throughout this specification.

[0259] Next, the electric potential of the reset signal inputted to thereset signal line RL is changed and the reset TFT 734 is placed in theOFF state. The standard electric potential of the sensor power sourceline VB is therefore not applied to the gate electrode of the buffer TFT735. Note that a period during which the reset TFT 734 is in the OFFstate is referred to as a sample period throughout this specification.

[0260] Note also that it is possible to drive an EL display having thesensor pixel shown in Embodiment 4 by a digital method and by an analogmethod. For a case of digital drive, it is preferable that the sampleperiod be longer than the address period Ta.

[0261] When light from the sensor EL element 732 is irradiated to thesensor TFT 736, the off current flows in a channel forming region of thesensor TFT 736. It is very important that the sensor TFT 736 be a bottomgate TFT. The electric potential of the gate electrode of the buffer TFT735 therefore changes in the sample period, and the size of the electricpotential change varies in accordance with the amount of off currentflowing in the channel forming region of the sensor TFT 736.

[0262] The off current flowing in the channel forming region of thesensor TFT 736 is proportional to the strength of light irradiated tothe sensor TFT 736 because the electric potential difference V_(GS)between the gate electrode and the source region of the sensor TFT 736is fixed. In other words, comparing when the luminance of the sensor ELelement 732 is high and when it is low, when the luminance is high, alarge off current flows in accordance with the channel forming region ofthe sensor TFT 736. Therefore, compared with when the luminance of thesensor EL element 732 is low, the changes in the electric potential ofthe gate electrode of the buffer TFT 735 become larger when theluminance is high.

[0263] The electric potential difference V_(GS) between the sourceregion and the gate electrode of the buffer TFT 735 is always fixed.Therefore, when the electric potential of the gate electrode of thebuffer TFT 735 changes, the electric potential of the source region ofthe buffer TFT 735 also changes in accordance with the gate electrodechange. The source region of the buffer TFT 735 is maintained at anelectric potential in which V_(GS) is subtracted from the electricpotential of the gate electrode of the buffer TFT 735.

[0264] The electric potential of the source region of the buffer TFT 735is applied to the sensor output wiring FL, and is inputted to acorrection circuit or a video signal correction circuit as a sensoroutput signal.

[0265] A cross sectional diagram of an EL display of Embodiment 4 havingthe sensor pixel 704 is shown in FIG. 16. In FIG. 16, reference numeral811 denotes a substrate and 812 denotes an insulating film which becomesa base (hereafter referred to as a base film). A transparent substrate,typically a glass substrate, a quartz substrate, a glass ceramicsubstrate, or a crystalline glass substrate can be used as the substrate811. Note that a material which can withstand the maximum processingtemperature attained during the manufacturing processes must be used.

[0266] Further, the base film 812 is particularly effective for a caseof using a substrate containing a mobile ion and a substrate havingconductivity need not be formed for a quartz substrate. An insulatingfilm containing silicon may be used as the base film 812. Note that an“insulating film containing silicon” indicates an insulating filmcontaining a predetermined ratio of oxygen and nitrogen with respect tosilicon, such as a silicon oxide film, a silicon nitride film, or asilicon oxynitride film (denoted by SiOxNy, where x and y are arbitraryintegers).

[0267] Reference numeral 735 denotes the buffer TFT, 734 denotes thereset TFT, 736 denotes the sensor TFT, 730 denotes the switching TFT,and 731 denotes the EL driving TFT. The buffer TFT 735, the switchingTFT 730, and the sensor TFT 736 are each formed by an n-channel TFT.Further, the reset TFT 734 and the EL driving TFT 731 are both formed bya p-channel TFT.

[0268] When the direction of EL light emitted is toward the substrateside, it is preferable that the switching TFT and the EL driving TFThave the above structure. However, the present invention is not limitedto this structure. The switching TFT and the EL driving TFT may ben-channel TFTs and may be p-channel TFTs. Furthermore, the reset TFT 734and the buffer TFT 735 may have mutually differing polarities, and maybe n-channel TFTs and may be p-channel TFTs. The sensor TFT 736 may alsobe an n-channel TFT or a p-channel TFT, provided that it has the samepolarity as the buffer TFT 735.

[0269] The switching TFT 730 has an active layer containing a sourceregion 813, a drain region 814, LDD regions 815 a to 815 d, a separationregion 816, and channel forming regions 817 a and 817 b; a gateinsulating film 818; gate electrodes 819 a and 819 b; a first interlayerinsulating film 820; a source wiring (source signal line) 821; a drainwiring 822; and channel forming region protective films 863 and 864.Note that the gate insulating film 818 and the first interlayerinsulating film 820 may be common among all TFTs on the substrate, ormay differ depending upon the circuit or the element.

[0270] Furthermore, the switching TFT 730 shown in FIG. 16 iselectrically connected to the gate electrodes 817 a and 817 b, becominga double gate structure. A multi-gate structure (a structure containingan active layer having two or more channel forming regions connected inseries) such as a triple gate structure, may of course also be used, inaddition to the double gate structure.

[0271] The multi-gate structure is extremely effective in reducing theoff current, and provided that the off current of the switching TFT issufficiently lowered, a capacitor connected to the gate electrode of theEL driving TFT 731 can have its capacitance reduced to the minimumnecessary. In other words, the surface area of the capacitor can be madesmaller, and therefore using the multi-gate structure is also effectivein expanding the effective light emitting surface area of the ELelements.

[0272] In addition, the LDD regions 815 a to 815 d are formed so as notto overlap the gate electrodes 819 a and 819 b through the gateinsulating film 818 in the switching TFT 730. This type of structure isextremely effective in reducing the off current. Furthermore, the length(width) of the LDD regions 815 a to 815 d may be set from 0.5 to 3.5 μm,typically between 2.0 and 2.5 μm.

[0273] Note that forming an offset region (a region which is asemiconductor layer having the same composition as the channel formingregion and to which the gate voltage is not applied) between the channelforming region and the LDD region is additionally preferable in a pointthat the off current is lowered. Further, when using a multi-gatestructure having two or more gate electrodes, the separation region 816(a region to which the same impurity element, at the same concentration,as that added to the source region or the drain region, is added)provided between the channel forming regions is effective in reducingthe off current.

[0274] Next, the EL driving TFT 731 is formed having an active layercontaining a source region 826, a drain region 827, and a channelforming region 829; the gate insulating film 818; a gate electrode 830,the first interlayer insulating film 820; a channel forming region 865;a source wiring 831; and a drain wiring 832.

[0275] Further, the drain region 814 of the switching TFT 730 isconnected to the gate 830 of the EL driving TFT 731. Although not shownin the figure, specifically the gate electrode 830 of the EL driving TFT731 is electrically connected to the drain region 814 of the switchingTFT 730 through the drain wiring (also referred to as a connectionwiring) 822. Note that the gate electrode 830 has a single gatestructure, but a multi-gate structure may also be used. Further, thesource wiring 831 of the EL driving TFT 731 is connected to a powersource supply line (not shown in the figure).

[0276] The EL driving TFT 731 is an element for controlling the amountof electric current injected to the EL element, and a relatively largeamount of current flows in the EL driving TFT 731. It is thereforepreferable to design the channel width W to be larger than the channelwidth of the switching TFT 730. Further, it is preferable to design thechannel length L such that an excess of electric current does not flowin the EL driving TFT 731. It is preferable to have from 0.5 to 2 μA(more preferably between 1 and 1.5 μA) per pixel.

[0277] In addition, by making the film thickness of the active layer(particularly the channel forming region) of the EL driving TFT 731thicker (preferably from 50 to 100 nm, even better between 60 and 80nm), degradation of the TFT may be suppressed. Conversely, in the caseof the switching TFT 730 it is also effective to make the film thicknessof the active layer (particularly the channel forming region) thinner(preferably from 20 to 50 nm, and more preferably between 25 and 40 nm)from the standpoint of making the off current smaller.

[0278] The buffer TFT 735, the reset TFT 734, and the sensor TFT 736have source wirings 845, 846, and 885, respectively. Further, theysimilarly have drain wirings 847, 848, and 887; gate electrodes 843,839, and 883; source regions 840, 835, and 880; channel forming regions842, 838, and 882; drain regions 841, 836, and 881; the gate insulatingfilm 818; the first interlayer insulating film 820; the channel formingregion protective films 861, 862, and 867; and LDD regions 844 a. 844 b,884 a, and 884 b respectively.

[0279] Note that in Embodiment 4, the LDD regions 844 a, 844 b, 884 a,and 884 b are formed in the buffer TFT 735 and the sensor TFT 736, but astructure having no LDD regions may also be used. Further, a structurehaving one LDD region in each source region side or drain region sidemay also be used.

[0280] There is almost no concern with degradation of the reset TFT 734,which is a p-channel TFT, due to hot carrier injection, and therefore noLDD region need be formed in particular. It is possible to take measuresagainst hot carrier injection by forming an LDD region similar to thatof the buffer TFT 735 and the sensor TFT 736, which is an n-channel TFT,of course.

[0281] Note that the channel forming region protective films 861 to 865are masks for forming the channel forming regions 842, 838, 817 a, 817b, 829, and 882. It is necessary for light to pass through the channelforming region protective films 861 to 865.

[0282] Next, reference numeral 849 denotes a first passivation film, andits film thickness may be set from 10 nm to 1 μm (preferably between 200and 500 nm). An insulating film containing silicon (in particular, it ispreferable to use a silicon oxynitride film or a silicon nitride film)can be used as the passivation film material. The passivation film 847possesses a role of protecting the TFTs from alkaline metals andmoisture. Alkaline metals such as sodium are contained in an EL layer854 formed on the final TFT (in particular, the EL driving TFT). Inother words, the first passivation film 849 works as a protecting layerso that these alkaline metals (mobile ions) do not penetrate into theTFT side.

[0283] Further, reference numeral 851 denotes a second interlayerinsulating film, which has a function as a leveling film for performingleveling of a step due to the TFTs. An organic resin film is preferableas the second interlayer insulating film 851, and one such as polyimide,polyamide, acrylic, or BCB (benzocyclobutene) may be used. These organicresin films have the advantages of easily forming a good, level surface,and having a low specific dielectric constant. The EL layer is extremelysensitive to unevenness, and therefore it is preferable to nearly absorbthe TFT step by the second interlayer insulating film 851. In addition,it is preferable to form the low specific dielectric constant materialthickly in order to reduce the parasitic capacitance formed between thegate signal wiring and the data signal wiring, and the cathode of the ELelement. The thickness, therefore, is preferably from 0.5 to 5 μm (morepreferably between 1.5 and 2.5 μm).

[0284] Further, reference numeral 852 denotes a pixel electrode (ananode of an EL element) made of a transparent conductive film. Afterforming a contact hole (opening) in the second interlayer insulatingfilm 851 and in the first passivation film 849, the pixel electrode 852is formed so as to be connected to the drain wiring 832 of the ELdriving TFT 731. Further, reference numeral 860 denotes a sensor wiringmade from a transparent conductive film, and after opening a contacthole (opening) in the second interlayer insulating film 851 and thefirst passivation film 849, the sensor wiring 860 is formed so as toconnect to the source wiring 885 of the sensor TFT 736 in the formedopening, at the same time as the pixel electrode 852. Note that if thepixel electrode 852 and the drain region 827 are formed so as to not bedirectly connected as in FIG. 16, then alkaline metals of the EL layercan be prevented from entering the active layer via the pixel electrode.

[0285] A third interlayer insulating film 853 is formed on the pixelelectrode 852 and the sensor wiring 860 from a silicon oxide film, asilicon nitride oxide film, or an organic resin film, with a thicknessfrom 0.3 to 1 μm. An opening is formed in the third interlayerinsulating film 853 over the pixel electrode 852 by etching, and theedge of the opening is etched so as to become a tapered shape. The taperangle may be set from 10 to 60°, (preferably between 30 and 50°).

[0286] An EL layer 854 is formed on the third interlayer insulating film853. A single layer structure or a lamination structure can be used forthe EL layer 854, but the lamination structure has good light emittingefficiency. In general, a hole injection layer, a hole transport layer,a light emitting layer, and an electron transport layer are formed inorder on the electrode, but a structure having a hole transport layer, alight emitting layer, and an electron transport layer, or a structurehaving a hole injection layer, a hole transport layer, a light emittinglayer, an electron transport layer, and an electron injection layer mayalso be used. Any known structure may be used by the present invention,and doping of a fluorescing pigment or the like into the EL layer mayalso be performed.

[0287] The structure of FIG. 16 is an example of a case of forming threetypes of EL elements corresponding to R, G, and B. Note that althoughonly one pixel is shown in FIG. 16, pixels having an identical structureare formed corresponding to red, green and blue colors, respectively,and that color display can thus be performed. It is possible toimplement the present invention without depending upon the method ofcolor display.

[0288] A cathode 855 of the EL element is formed on the EL layer 854 asan opposing electrode. A material containing a low work coefficientmaterial such as magnesium (Mg), lithium (Li), or calcium (Ca), is usedas the cathode 855. Preferably, an electrode made from MgAg (a materialmade from Mg and Ag at a mixture of Mg:Ag =10:1) is used. In addition, aMgAgAl electrode, an LiAl electrode, and an LiFAI electrode can be givenas other examples.

[0289] It is preferable to form the cathode 855 in succession, withoutexposure to the atmosphere, after forming the EL layer 854. This isbecause the interface state between the cathode 855 and the EL layer 854greatly influences the light emitting efficiency of the EL element. Notethat, throughout this specification, a light emitting element formed bya pixel electrode (anode), an EL layer, and a cathode is referred to asan EL element. Note also that FIG. 16 shows a cross sectional diagram ofthe sensor pixel, and therefore a location in which the pixel electrode852, the EL layer 854, and the opposing electrode 855 are surrounded bya dotted line is the sensor EL element 732.

[0290] The lamination body composed of the EL layer 854 and the cathode855 must be formed separately for each pixel, but the EL layer 854 isextremely weak with respect to moisture, and consequently a normalphotolithography technique cannot be used. It is therefore preferable touse a physical mask material such as a metal mask, and to selectivelyform the layers by a gas phase method such as vacuum evaporation,sputtering, or plasma CVD.

[0291] Note that it is also possible to use a method such as ink jetprinting or screen printing as the method of selectively forming the ELlayer 854. However, the cathode cannot currently be formed in successionwith these methods, and therefore it is preferable to use the othermethods stated above.

[0292] Further, a protecting electrode may also be formed on theopposing electrode 855. The protecting electrode protects the cathode855 from external moisture and the like, and at the same time is anelectrode for connecting the cathodes 855 of each pixel. It ispreferable to use a low resistance material containing aluminum (Al),copper (Cu), or silver (Ag) as the protecting electrode. The protectingelectrode can also be expected to have a heat radiating effect whichrelieves the amount of heat generated by the EL layer. Further, it iseffective to form the protecting electrode in succession, withoutexposure to the atmosphere, after forming the EL layer 854 and thecathode 855.

[0293] Note that it goes without saying that all of the TFTs shown inFIG. 16 may have a polysilicon film as their active layer.

[0294] The present invention is not limited to the structure of the ELdisplay of FIG. 16, and the structure of FIG. 16 is only one preferredembodiment for implementing the present invention.

[0295] Embodiment 5

[0296] An example of an external view of an EL display of the presentinvention is explained in Embodiment 5.

[0297]FIG. 17A is a top view of an EL display of the present invention.In FIG. 17A, reference numeral 4010 denotes a substrate, referencenumeral 4011 denotes a display portion, reference numeral 4012 denotes asource signal line driver circuit, and reference numeral 4013 denotes agate signal line driver circuit. The driver circuits are connected to anexternal device via wirings 4014 to 4016, which lead to an FPC 4017.

[0298] Further, a sensor portion 4019 is connected to the displayportion 4011 in by a wiring 4020, and is connected to a correctioncircuit or a video signal correction circuit provided outside thesubstrate by a wiring 4018 leading to the FPC 4017. Note that althoughthe correction circuit, or the video signal correction circuit, isprovided outside the substrate in Embodiment 5, the present invention isnot limited to such, and the correction circuit, or the video signalcorrection circuit, may be provided on the substrate.

[0299] A cover member 6000, a sealing member (also referred to as ahousing material) 7000, and a sealant (a second sealing member) 7001 areprovided at this point so as to surround at least the display portion4011 and the sensor portion 4019, and preferably to surround the drivercircuits 4012 and 4013, the sensor portion 4019, and the display portion4011.

[0300] Further, FIG. 17B shows in cross section the structure of the ELdisplay of Embodiment 5, and a driver circuit TFT (note that a CMOScircuit combining an n-channel TFT and a p-channel TFT is shown here)4022 and a TFT of a display pixel (note that only an EL driving TFT forcontrolling the electric current to an EL element is shown here) 4023are formed on the substrate 4010 and a base film 4021. Note that a TFTof a sensor pixel is not shown in the figure here. These TFTs have aknown structure (a top gate structure or a bottom gate structure).

[0301] After the driver circuit TFT 4022 and the EL driver circuit TFT4023 are completed using a known method of manufacture, a pixelelectrode 4027 made from a transparent conductive film electricallyconnected to a drain of the EL driving TFT 4023 is formed on aninterlayer insulating film (leveling film) 4023 made from a resinmaterial. A compound of indium oxide and tin oxide (referred to as ITO)or a compound of indium oxide and zinc oxide can be used as thetransparent conductive film. An insulating film 4028 is formed once thepixel electrode is formed, and an opening is formed on the pixelelectrode 4027.

[0302] An EL layer 4029 is formed next. A lamination structure obtainedby freely combining known EL materials (a hole injection layer, a holetransport layer, a light emitting layer, an electron transport layer,and an electron injection layer), or a single layer structure, may beused for the EL layer 4029. A known technique may be used to form such astructure. Further, there are low molecular weight materials and highmolecular weight materials (polymer materials) among the EL materialsform forming the EL layer. An evaporation method is used when a lowmolecular weight material is used, while it is possible to use a simplemethod such as printing, or ink-jet method when a high molecular weightmaterial is used.

[0303] The EL layer is formed by evaporation using a shadow mask inEmbodiment 5. Color display becomes possible by forming light emittinglayers (a red color light emitting layer, a green color light emittinglayer, and a blue color light emitting layer) capable of emitting lightat different wavelength for each pixel using the shadow mask. Inaddition, a method of combining a color changing layer (CCM) and a colorfilter, and a method of combining a white color light emitting layer anda color filter are available, and both may be used. A single color lightemitting EL display can also be made, of course.

[0304] After forming the EL layer 4029, a cathode 4030 is formed on top.It is preferable to remove as much moisture and oxygen as possible fromthe interface between the cathode 4030 and the EL layer 4029. A methodin which the EL layer 4029 and the cathode 4030 are formed in successionwithin a vacuum, or a method in which the EL layer 4029 is formed in aninert atmosphere and the cathode 4030 is then formed without exposure tothe atmospheric air is therefore necessary. The above film formation canbe performed by using a multi-chamber method (cluster chamber method)film formation apparatus.

[0305] Note that a lamination structure of a LiF (lithium fluoride) filmand an Al (aluminum) film is used as the cathode 4030 in Embodiment 5.Specifically, a 1 nm thick LiF (lithium fluoride) film is formed byevaporation on the EL layer 4029, and a 300 nm thick aluminum film isformed on the LiF film. An MgAg electrode, which is a known cathodematerial, may of course be used instead. The cathode 4030 is thenconnected to the wiring 4016 in a region denoted by reference numeral4031. The wiring 4016 is an power source supply line for applying apredetermined voltage to the cathode 4030, and is connected to the FPC4017 through a conductive paste material 4032.

[0306] The cathode 4030 and the wiring 4016 are electrically connectedin the region shown by reference numeral 4031, and therefore it isnecessary to form contact holes in the interlayer insulating film 4026and in the insulating film 4028. These contact holes may be formedduring etching of the interlayer insulating film 4026 (when the pixelelectrode contact hole is formed) and during etching of the insulatingfilm 4028 (when forming the opening before forming the EL layer).Further, the contact holes may also be formed by etching in one shotthrough the interlayer insulating film 4026 when etching the insulatingfilm 4028. A contact hole having a good shape can be formed in this caseprovided that the interlayer insulating film 4026 and the insulatingfilm 4028 are formed from the same resin material.

[0307] A passivation film 6003, a filler material 6004 and the covermember 6000 are formed covering the surface of the EL element thusformed.

[0308] In addition, the sealing member 7000 is formed in a space definedby the cover member 6000 and the substrate 4010 so as to surround the ELelement containing the pixel electrode 4027, the EL layer 4029, and thecathode 4030. The sealant (the second sealing member) 7001 is formed onthe outside of the sealing member 7000.

[0309] Further, a filler 6004 is provided so as to cover the EL element.The filler 6004 also functions as an adhesive for bonding a cover member6000. As the filler 6004, PVC (polyvinyl chloride), epoxy resin,silicone resin, PVB (polyvinyl butyral) or EVA (ethylene-vinyl acetate)may be used. Preferably, a desiccant is provided in the filler 6004 tomaintain a moisture absorbing effect.

[0310] The filler 6004 may also contain a spacer. The spacer may beparticles of BaO or the like so that the spacer itself has a moistureabsorbing effect.

[0311] If a spacer is provided, the passivation film 6003 can reduce thespacer pressure. A resin film or the like may also be providedindependently of the passivation film to reduce the spacer pressure.

[0312] As the cover member 6000, a glass sheet, an aluminum sheet, astainless steel sheet, an FRP (fiberglass-reinforced plastic) sheet, aPVF (polyvinyl fluoride) film, a Mylar film, a polyester film, anacrylic film, or the like may be used. If PVB or EVA is used as thefiller 6004, it is preferable to use a sheet having a structure in whichan aluminum foil having a thickness of several tens of μm is sandwichedbetween PVF or Mylar films.

[0313] Some setting of the direction of luminescence from the EL element(the direction in which light is emitted) necessitates making the covermember 6000 transparent.

[0314] Also the wiring 4016 is electrically connected to the FPC(flexible printed circuit) 4017 by being passed through a gap betweenthe sealing member 7000, the sealant 7001, and the substrate 4010. Whilethe electrical connection of the wiring 4016 has been described, otherwirings 4014, 4015, and 4018 are also connected electrically to the FPC4017 by being passed under the sealing member 7000 and the sealant 7001.

[0315] In Embodiment 5, after the filler 6004 has been provided, thecover member 6000 is bonded and the sealing member 7000 is attached soas to cover the side surfaces (exposed surfaces) of the filler 6004.However, the filler 6004 may be provided after attachment of the covermember 6000 and the sealing member 7000. In such a case, a fillerinjection hole is formed which communicates with a cavity formed by thesubstrate 4010, the cover member 6000 and the sealing member 7000. Thecavity is evacuated to produce a vacuum (at 10-2 Torr or lower), theinjection hole is immersed in the filler in a bath, and the air pressureoutside the cavity is increased relative to the air pressure in thecavity, thereby filling the cavity with the filler.

[0316] Embodiment 6

[0317] An example of an external view of an EL display of the presentinvention, differing from that of Embodiment 5, is explained inEmbodiment 6 with reference to FIGS. 18A and 18B. Reference numeralswhich are the same as those of FIGS. 17A and 17B denote the samecomponents, and therefore an explanation of these components is omitted.

[0318]FIG. 18A is a top view of the EL display of Embodiment 6, and FIG.18B is a cross-sectional view taken along the line A-A′ in FIG. 18A.

[0319] Internal portions of the EL device below a passivation film 6003which covers a surface of the EL element are formed in the same manneras Embodiment 5.

[0320] The filler 6004 also functions as an adhesive for bonding a covermember 6000. As the filler 6004, PVC (polyvinyl chloride), epoxy resin,silicone resin, PVB (polyvinyl butyral) or EVA (ethylene-vinyl acetate)may be used. Preferably, a desiccant is provided in the filler 6004 tomaintain a moisture absorbing effect.

[0321] The filler 6004 may also contain a spacer. The spacer may beparticles of BaO or the like so that the spacer itself has a moistureabsorbing effect.

[0322] If a spacer is provided, the passivation film 6003 can reduce thespacer pressure. A resin film or the like may also be providedindependently of the passivation film to reduce the spacer pressure.

[0323] As the cover member 6000, a glass sheet, an aluminum sheet, astainless steel sheet, an FRP (fiberglass-reinforced plastic) sheet, aPVF (polyvinyl fluoride) film, a Mylar film, a polyester film, anacrylic film, or the like may be used. If PVB or EVA is used as thefiller 6004, it is preferable to use a sheet having a structure in whichan aluminum foil having a thickness of several tens of Aim is sandwichedbetween PVF or Mylar films.

[0324] Some setting of the direction of luminescence from the EL element(the direction in which light is emitted) necessitates making the covermember 6000 transparent.

[0325] Next, the cover member 6000 is bonded by using the filler 6004.Thereafter, a frame member 6001 is attached so as to cover side surfaces(exposed surfaces) of the filler 6004. The frame member 6001 is bondedby a sealing member 6002 (functioning as an adhesive). Preferably, aphoto-setting resin is used as the sealing member 6002. However, athermosetting resin may be used if the heat resistance of the EL layeris high enough to allow use of such a resin. It is desirable that thesealing member 6002 has such properties as to inhibit permeation ofmoisture and oxygen as effectively as possible. A desiccant may be mixedin the sealing member 6002.

[0326] Also wiring 4016 is electrically connected to a flexible printedcircuit (FPC) 4017 by being passed through a gap between the sealingmember 6002 and the substrate 4010. While the electrical connection ofthe wiring 4016 has been described, other wirings 4014, 4015 and 4018are also connected electrically to the FPC 4017 by being passed underthe sealing member 6002.

[0327] In Embodiment 6, after the filler 6004 has been provided, thecover member 6000 is bonded and the frame member 6001 is attached so asto cover the side surfaces (exposed surfaces) of the filler 6004.However, the filler 6004 may be provided after attachment of the covermember 6000, the sealing member 6002, and the frame member 6001. In sucha case, a filler injection hole is formed which communicates with acavity formed by the substrate 4010, the cover member 6000,the sealingmember 6002, and the frame member 6001. The cavity is evacuated toproduce a vacuum (at 10⁻² Torr or lower), the injection hole is immersedin the filler in a bath, and the air pressure outside the cavity isincreased relative to the air pressure in the cavity, thereby fillingthe cavity with the filler.

[0328] Embodiment 7

[0329] A more detailed cross sectional structure of a display portion inan EL display is shown in FIG. 19, a top structure thereof is shown inFIG. 20A, and a circuit diagram thereof is shown in FIG. 20B. Commonsymbols are used in FIG. 19 and FIGS. 20A and 20B, and therefore theymay be mutually referenced.

[0330] In FIG. 19, a switching TFT 3502 formed on a substrate 3501 is ann-channel TFT formed by a known method. A double gate structure is usedin Embodiment 7, but there are no large differences in the structure andthe manufacturing process, and therefore an explanation is omitted. Notethat by using the double gate structure, in effect this becomes astructure in which two TFTs are connected in series, which has theadvantage of being capable of reducing the value of the off current.Note also that although the double gate structure is used in Embodiment7, a single gate structure and a triple gate structure may also be used,and a multi-gate structure possessing more than three gates may also beused. Furthermore, a p-channel TFT formed by using a known method mayalso be used.

[0331] An n-channel TFT formed by a known method is used as an ELdriving TFT 3503. A drain wiring 35 of the switching TFT 3502 iselectrically connected to a gate electrode 37 of the EL driving TFT 3503by a wiring 36. Further, a wiring denoted by reference numeral 38 is agate wiring for electrically connecting gate electrodes 39 a and 39 b ofthe. switching TFT 3502.

[0332] The EL driving TFT 3503 is an element for controlling the amountof electric current flowing in a display EL element, and therefore muchcurrent flows therein. Therefore the EL driving TFT 3503 is an elementhaving a high risk of deterioration due to heat and due to hot carriers.An LDD region overlapping the gate electrode through a gate insulatingfilm may therefore be provided on the drain side of the EL driving TFT3503, through which deterioration due to heat and due to hot carriers isprevented.

[0333] The EL driving TFT 3503 having a single gate structure is shownin the figures in Embodiment 7, but a multi-gate structure in which aplurality of TFTs are connected in series may also be used. In addition,a structure in which a plurality of TFTs are connected in parallel andsubstantially dividing a channel forming region into a plurality ofchannel forming regions, so that heat can be released with highefficiency may also be used. This type of structure is effective as ameasure against deterioration due to heat.

[0334] Furthermore, as shown in FIG. 20A, the wiring 36 which includesthe gate electrode 37 of the EL driving TFT 3503 overlaps with a drainwiring 40 of the EL driving TFT 3503 through the insulating film in aregion denoted by reference numeral 3504. A storage capacitance isformed in the region shown by reference numeral 3504 at this point. Thestorage capacitance 3504 is formed from a semiconductor film 3520 whichis electrically connected to an power source supply line 3506, aninsulating film (not shown in the figures) on the same layer as the gateinsulating film, and the wiring 36. Further, it is also possible to usea capacitor formed from the wiring 36, the same layer (not shown in thefigures) as that of a first interlayer insulating film, and the powersource supply line 3506 as a storage capacitance. The storagecapacitance 3504 functions as a capacitor for storing a voltage appliedto the gate electrode 37 of the EL driving TFT 3503. Note that the drainof the EL driving TFT 3503 is connected to the power source supply line(power source supply line) 3506, and a fixed voltage is always applied.

[0335] A first passivation film 41 is formed on the switching TFT 3502and the EL driving TFT 3503, and a leveling film 42 is formed on top ofthat from an insulating resin film. It is extremely important to levelthe step due to the TFTs using the leveling film 42. An EL layer formedlater is extremely thin, so there are cases in which defective lightemissions occur because of the presence of the step. Therefore, to formthe EL layer on as level a surface as possible, it is preferable toperform leveling before forming a pixel electrode.

[0336] Furthermore, reference numeral 43 denotes a pixel electrode(display EL element cathode) made from a conductive film with highreflectivity, and this is electrically connected to a drain region ofthe EL driving TFT 3503. It is preferable to use for the pixel electrode43 a low resistance conductive film, such as an aluminum alloy film, acopper alloy film, and a silver alloy film, or a laminate of such films.Of course, a lamination structure with another conductive film may alsobe used.

[0337] In addition, a light emitting layer 45 is formed in the middle ofa groove (corresponding to a pixel) formed by banks 44 a and 44 b, whichare formed of insulating films (preferably resins). In FIG. 20A, thebanks are partially omitted in order to clarify the position of thestorage capacitance 3504, showing only the banks 44 a and 44 b. However,the banks are provided between pixels so as to partially cover the powersource supply line 3506 and the source wiring 34. Note that only twopixels are shown in the figures here, but light emitting layers may beformed so as to correspond to the colors R (red), G (green), and B(blue), respectively. A n conjugate polymer type material is used as anorganic EL material. PPV(Polyparaphenylene vinylene) type, PVK(polyvinyl carbazole) type, and polyfluorene type can be given astypical polymer type materials.

[0338] Note that there are several kinds of PPV type organic ELmaterials, and materials disclosed in Shenk, H., Becker, H., Gelsen, O.,Kluge, E., Kreuder, W., and Spreitzer, H., “Polymers for Light EmittingDiodes”, Euro Display Proceedings, 1999, pp. 33-7, and in JapanesePatent Application Laid-open No. Hei 10-92576, for example, may be used.

[0339] As specific light emitting layers, cyano-polyphenylene vinylenemay be used as a red light emitting layer, polyphenylene vinylene may beused as a green light emitting layer, and polyphenylene vinylene orpolyalkylphenylene may be used as a blue light emitting layer. The filmthicknesses may be between 30 and 150 nm (preferably between 40 and 100nm).

[0340] However, the above is an example of the organic EL materialswhich can be used as light emitting layers, and it is not necessary tobe limited to these materials. An EL layer (a layer for emitting lightand for moving carriers for light emission) may be formed by freelycombining light emitting layers, an electric charge transport layer, andan electric charge injection layer.

[0341] For example, Embodiment 7 shows an example of using a polymertype material as a light emitting layer, but a low molecular weightorganic EL material may also be used. Further, it is possible to useinorganic materials such as silicon carbide, as an electric chargetransport layer or an electric charge injection layer. Known materialscan be used for these organic EL materials and inorganic materials.

[0342] A lamination structure EL layer, in which a hole injection layer46 made from PEDOT (polythiophene) or PAni (polyaniline) is formed onthe light emitting layer 45, is used in Embodiment 7. An anode 47 isthen formed on the hole injection layer 46 from a transparent conductivefilm. The light generated by the light emitting layer 45 is radiatedtoward the upper surface (toward the top of the TFT) in Embodiment 7,and therefore the anode must be light-transmissive. An indium oxide andtin oxide compound, or an indium oxide and zinc oxide compound can beused for the transparent conductive film. However, because it is formedafter forming the low heat resistance light emitting layer and holeinjection layer, it is preferable to use a material which can bedeposited at as low a temperature as possible.

[0343] An EL element 3505 is completed at the point where the anode 47is formed. Note that what is called the EL element 3505 here is acapacitor formed of the pixel electrode (cathode) 43, the light emittinglayer 45, the hole injection layer 46, and the anode 47. The pixelelectrode 43 is nearly equal in area to the pixel, and consequently theentire pixel functions as an EL element. Therefore, the light emissionefficiency is extremely high, and a bright image display becomespossible.

[0344] In addition, a second passivation film 48 is then formed on theanode 47 in Embodiment 7. It is preferable to use a silicon nitride filmor a silicon oxynitride film as the second passivation film 48. Thepurpose of this is the isolation of the display EL element from theoutside, and this for preventing degradation due to oxidation of theorganic EL material, as well as for controlling degas from the organicEL material. The reliability of the EL display can thus be raised.

[0345] The EL display panel of the present invention has a displayportion formed of pixels structured as in FIG. 19, and has a switchingTFT with a sufficiently low off current value, and an EL driving TFTwhich is strong against hot carrier injection. An EL display which hashigh reliability and which is capable of displaying a good image cantherefore be obtained.

[0346] Note that it is possible to implement the constitution ofEmbodiment 4by freely combining it with the constitutions of theembodiment mode and Embodiment 1.

[0347] Embodiment 8

[0348] A structure in which the structure of the display EL element 3505in the pixel portion shown in Embodiment 7 is inverted is explained inEmbodiment 8. FIG. 21 is used in the explanation. Note that the onlypoints of difference between the structure of FIG. 21 and that of FIG.19 is the display EL element and the EL driving TFT 3503, and thereforean explanation of other portions is omitted.

[0349] An EL driving TFT 3503 in FIG. 21 is a p-channel TFT manufacturedby using a known method. Refer to the manufacturing process ofEmbodiment 2 in forming the p-channel TFT.

[0350] A transparent conductive film is used as a pixel electrode(anode) 50 in Embodiment 5. Specifically, a conductive film made from acompound of indium oxide and zinc oxide is used. Of course, a conductivefilm made from a compound of indium oxide and tin oxide may also beused.

[0351] After then forming banks 51 a and 51 b from insulating films, alight emitting layer 52 is formed from polyvinyl carbazole by solutioncoating. An electron injection layer 53 is formed on the light emittinglayer from potassium acetylacetonate (expressed as acacK), and a cathode54 is formed from an aluminum alloy. In this case the cathode 54 alsofunctions as a passivation film. A display EL element 3701 is thusformed.

[0352] The light generated by the light emitting layer 52 is radiatedtoward the substrate on which the TFT is formed in Embodiment 8, asshown by the arrows.

[0353] Note that it is possible to implement the constitution ofEmbodiment 5 by freely combining it with the constitution of any ofEmbodiments 1 to 3.

[0354] Embodiment 9

[0355] In Embodiment 9, an example of a case of a pixel having astructure which differs from that of the circuit diagram shown in FIG.20B is shown in FIGS. 22A to 22C. Note that, in Embodiment 9, referencenumeral 3801 denotes a source signal line which is a portion of a sourcewiring of a switching TFT 3802, reference numeral 3803 denotes a gatesignal line which is a portion of a gate wiring of a switching TFT 3802,reference numeral 3804 denotes an EL driving TFT, 3805 denotes acapacitor, 3806 and 3808 are power source supply lines, and referencenumeral 3807 denotes a display EL element.

[0356]FIG. 22A is an example of a case in which the power source supplyline 3806 is common between two pixels. The case of FIG. 22A ischaracterized in that two pixels are formed so as to be symmetric withrespect to the power source supply line 3806. In this case the number ofpower source supply lines can be reduced, and a display portion can haveeven higher definition.

[0357] Further, FIG. 22B is an example of a case of forming the powersource supply line 3808 in parallel with the gate signal line 3803. Notethat FIG. 22B has a structure in which the power source supply line 3808and the gate signal line 3803 are formed so as not to overlap, butprovided that the two are formed on differing layers, they can be formedso as to overlap through an insulating film. In this case the surfacearea occupied by the power source supply line 3808 and the gate signalline 3803 can be shared, and therefore the display portion can have evenhigher definition.

[0358] In addition, FIG. 22C has a structure characterized in that thepower source supply line 3808 is formed in parallel to the gate signallines 3803 as in the structure shown in FIG. 22B, and in addition, twopixels are formed so as to be symmetric with respect to the power sourcesupply line 3808. Furthermore, it is also effective to form the powersource supply line 3808 so as to overlap with one of the gate signallines 3803. In this case the number of power source supply lines can bereduced, and the display portion can have even higher definition.,

[0359] Note that it is possible to implement the constitution ofEmbodiment 9 by freely combining with the constitution of any of theembodiment mode and Embodiments 1 to 6 and 8. Furthermore, it iseffective to use the EL display having the pixel structure of Embodiment9 as a display device of electronic equipment in Embodiment 11.

[0360] Embodiment 10

[0361] A structure in which a storage capacitance for maintaining avoltage applied to a gate electrode of an EL driving TFT is omitted isexplained in Embodiment 10. For a case in which the EL driving TFT is ann-channel TFT and has an LDD region formed so as to overlap with thegate electrode through a gate insulating film, a parasitic capacitancegenerally referred to as a gate capacitor is formed in the overlappingregion. This parasitic capacitor is actively used as a substitute for astorage capacitance, which characterizes Embodiment 10.

[0362] The capacitance of the parasitic capacitor changes in accordancewith the surface area in which the gate electrode and the LDD regionoverlap, and is determined by the length of the LDD region included inthe overlapping region.

[0363] Further, it is also possible to similarly omit the storagecapacitance in the structures of FIGS. 22A, 22B, and 22C shown inEmbodiment 9.

[0364] Note that it is possible to implement the constitution ofEmbodiment 10 by freely combining it with the constitution of any ofEmbodiments 1 to 9. Further, it is effective to use the EL displayhaving the pixel structure of Embodiment 10 as a display device ofelectronic equipment in Embodiment 11.

[0365] Embodiment 11

[0366] The present invention is not limited to a structure in which alight receiving diode in a sensor pixel detects only the luminance oflight emitted from a sensor EL element. The light receiving diode of thesensor pixel may also detect the luminance of light from outside of anEL display (external light) in addition to the luminance of the light ofthe sensor EL element, and correction of the luminance of the EL elementmay be performed by adjusting to the external luminance. For instance,correction is made such that the luminance of the EL element is loweredwhen the luminance of the external light is high, and when the luminanceof the external light is low, on the other hand, the EL elementincreases its luminance.

[0367] According to the above structure, a clear image can be displayedirrespective of the luminance of the surroundings.

[0368] Embodiment 12

[0369] An EL display of the present invention in which the structure ofa sensor pixel differs from that shown in the embodiment mode, andEmbodiments 1 to 4 as described.

[0370] A circuit diagram of a sensor pixel of Embodiment 12 is the sameas that of the EL display shown in the embodiment mode, and thereforeFIG. 3 is referenced. The structure of a light receiving diode inEmbodiment 12 differs from that of the embodiment mode. A crosssectional diagram of a sensor pixel of Embodiment 12 is shown in FIG. 25in order to explain the structure of the light receiving diode ofEmbodiment 12.

[0371] Reference numeral 935 denotes a buffer TFT, reference numeral 934denotes a reset TFT, 936 denotes a light receiving diode, 930 denotes aswitching TFT, 931 denotes an EL driving TFT, and reference numeral 932denotes a sensor EL element.

[0372] The light receiving diode 936 has an anode 980, a cathode 981, achannel forming region 983, a buffer region 984, an anode wiring 985,and a cathode wiring 986 within an active layer.

[0373] The anode 980 and the cathode 981 of Embodiment 12 are formed bydoping a p-type impurity or an n-type impurity to an essentiallyintrinsic semiconductor body. Note that the polarity of the impurityadded to the anode 980 and to the cathode 981 is the same. Further, theimpurity added to the anode 980 and to the cathode 981 is added to thebuffer region 984 at a concentration which is lower than that in theanode 980 and in the cathode 981.

[0374] It is preferable that the polarity of the impurity added to asource region and a drain region of the buffer TFT 935 be the same asthat of the impurity added to the anode 980 and to the cathode 981 ofthe light receiving diode 936. The cathode 981 of the light receivingdiode 936 is electrically connected to a drain region of the reset TFT934 and to a gate electrode of the buffer TFT 935. The anode 980 of thelight receiving diode 936 is maintained at a fixed electric potential.

[0375] Electric current flows in the light receiving diode 936 when thelight receiving diode 936 is irradiated with light from the sensor ELelement 932. The electric potential of the gate electrode of the bufferTFT 935, which is fixed during the reset period, therefore changes inthe sample period, and the amount of change of the electric potentialchanges in accordance with the amount of the electric current flowing inthe light receiving diode 936.

[0376] The electric current flowing in the light receiving diode 936 isproportional to the intensity of the light irradiating the lightreceiving diode 936. Namely, comparing when the luminance of the lightof the sensor EL element 932 is high and when it is low, when theluminance is high a large off current flows in the light receiving diode936. The changes in the electric potential of the gate electrode of thebuffer TFT 935 therefore is larger when the luminance of the light ofthe sensor EL element 932 is high compared to when the luminance thereofis low.

[0377] The electric potential difference V_(GS) between the sourceregion and the gate electrode of the buffer TFT 935 is always fixed, andtherefore the source region of the buffer TFT 935 is maintained at anelectric potential in which V_(GS) is subtracted from the electricpotential of the gate electrode of the buffer TFT 935. When the electricpotential of the gate electrode of the buffer TFT 935 changes, theelectric potential of the source region of the buffer TFT 935 alsochanges in accompaniment.

[0378] The electric potential of the source region of the buffer TFT 935is given to a sensor output wiring FL, and is inputted to a correctioncircuit or a video signal correction circuit as a sensor output signal.

[0379] Without newly adding new manufacturing steps for the lightreceiving diode, the light receiving diode can be formed simultaneouslywith the other TFTs and the number of steps for manufacturing the ELdisplay can be reduced with Embodiment 12.

[0380] Embodiment 13

[0381] An EL display device formed by implementing the present inventionhas superior visibility in bright locations in comparison to a liquidcrystal display device because it is a self-emissive type device, andmoreover its field of vision is wide. Accordingly, it can be used as adisplay portion for various electronic devices. For example, it isappropriate to use the EL display device of the present invention as adisplay portion of an EL display (a display incorporating the EL displaydevice in its casing) having a diagonal equal to 30 inches or greater(typically equal to 40 inches or greater) for appreciation of TVbroadcasts by large screen.

[0382] Note that all displays exhibiting (displaying) information suchas a personal computer display, a TV broadcast reception display, or anadvertisement display are included as the EL display device. Further,the EL display device of the present invention can be used as a displayportion of the other various electronic devices.

[0383] The following can be given as examples of such electronicdevices: a video camera; a digital camera; a goggle type display (headmounted display): a car navigation system; an audio reproducing device(such as a car audio system, an audio compo system); a notebook personalcomputer; a game equipment; a portable information terminal (such as amobile computer, a mobile telephone, a mobile game equipment or anelectronic book); and an image playback device provided with a recordingmedium (specifically, a device which performs playback of a recordingmedium and is provided with a display which can display those images,such as a digital versatile disk (DVD)). In particular, because portableinformation terminals are often viewed from a diagonal direction, thewideness of the field of vision is regarded as very important. Thus, itis preferable that the EL display device is employed. Examples of theseelectronic devices are shown in FIGS. 23A to 24B.

[0384]FIG. 23A is an EL display, containing a casing 2001, a supportstand 2002, a display portion 2003 and a sensor portion 2004. Thepresent invention can be used in the display portion 2003 and a sensorportion 2004. Since the EL display is a self-emissive type devicewithout the need of a backlight, its display portion can be made thinnerthan a liquid crystal display device.

[0385]FIG. 23B is a video camera, containing a main body 2101, a displayportion 2102, an audio input portion 2103, operation switches 2104, abattery 2105, an image receiving portion 2106 and a sensor portion 2107.The EL display device of the present invention can be used in thedisplay portion 102 and a sensor portion 2107.

[0386]FIG. 23C is a portion of a head fitting type EL display (rightside), containing a main body 2201, a signal cable 2202, a head fixingband 2203, a display portion 2204, an optical system 2205, an EL displaydevice 2206 and a sensor portion 2207. The present invention can be usedin the EL display device 2206 and a sensor portion 2207.

[0387]FIG. 23D is an image playback device (specifically, a DVD playbackdevice) provided with a recording medium, containing a main body 2301, arecording medium (such as a DVD) 2302, operation switches 2303, adisplay portion (a) 2304, a display portion (b) 2305 and a sensorportion 2306. The display portion (a) 2304 is mainly used for displayingimage information, and the image portion (b) 23(05 is mainly used fordisplaying character information, and the EL display device of thepresent invention can be used in the image portion (a) 2304, in theimage portion (b) 2305 and in the sensor portion 2306. Note thatdomestic game equipment is included as the image playback deviceprovided with a recording medium.

[0388]FIG. 23E is a goggle type display (head mounted display),containing a main body 2401, a display portion 2402, an arm portion 2403and a sensor portion 2404. The present invention can be used in thedisplay portion 2402 and the arm portion 2403. In the FIG. 23E, while asensor portion 2404 is provided in an arm portion 2403, the presentinvention is not limited to the structure. The sensor portion 2404 canbe provided in a row with the display portion 2402.

[0389]FIG. 23F is a personal computer, containing a main body 2501, acasing 2502, a display portion 2503, a keyboard 2504 and a sensorporting 2505. The EL display device of the present invention can be usedin the display portion 2503 and a sensor portion 2505.

[0390] Note that in the future if the emission luminance of EL materialsbecomes higher, the projection of light, including output images can beenlarged by lenses or the like. Then it will become possible to use theEL display device of the present invention in a front type or a reartype projector.

[0391] The above electronic devices are becoming more often used todisplay information provided through an electronic transmission circuitsuch as the Internet or CATV (cable television), and in particular,opportunities for displaying animation information are increasing. Theresponse speed of EL materials is extremely high, and therefore the ELdisplay device is favorable for performing animation display.

[0392] The emitting portion of the EL display device consumes power, andtherefore it is preferable to display information so as to have theemitting portion become as small as possible. Therefore, when using theEL display device in a display portion which mainly displays characterinformation, such as a portable information terminal, in particular, aportable telephone and an audio reproducing device, it is preferable todrive it by setting non-emitting portions as background and formingcharacter information in emitting portions.

[0393]FIG. 24A is a portable telephone, containing a main body 2601, anaudio output portion 2602, an audio input portion 2603, a displayportion 2604, operation switches 2605, an antenna 2606 and a sensor2607. The EL display device of the present invention can be used in thedisplay portion 2604 and the sensor 2607. Note that by displaying whitecharacters in a black background in the display portion 2604, the powerconsumption of the portable telephone can be reduced.

[0394]FIG. 24B is an audio reproducing device, specifically a car audiosystem, containing a main body 2701, a display portion 2702, andoperation switches 2703, 2704 and a sensor portion 2705. The EL displaydevice of the present invention can be used in the display portion 2702and a sensor portion 2705. Furthermore, an audio reproducing device fora car is shown in this embodiment, but it may also be used for a mobiletype and a domestic type of audio reproducing device. Note that bydisplaying white characters in a black background in the display portion2704, the power consumption can be reduced. This is particularlyeffective in a mobile type audio reproducing device.

[0395] The range of applications of the present invention is thusextremely wide, and it is possible to apply the present invention toelectronic devices in all fields. Furthermore, any constitution of theEL display device shown in Embodiments 1 to 12 may be employed in theelectronic devices of this embodiment.

[0396] According to the present invention, even if the speed ofdeterioration of an EL layer is influenced by factors such as thestructure of a device driving an EL display, the properties of an ELmaterial structuring the EL layer, an electrode material, the conditionsin the manufacturing process, and a method of driving the EL display, anEL display capable of displaying a clear image having a desired colorcan be provided.

[0397] Further, by forming a display EL element and a sensor EL elementat the same conditions and at the same time, the speed of deteriorationof the EL layers of the display EL element and of the sensor EL elementcan be made the same. Therefore, the luminance of the sensor EL elementwhich a light receiving diode detects becomes very close to theluminance of the display EL element, and changes in the luminance of thedisplay EL element can be more accurately detected, making it possibleto correct to obtain desired luminance.

[0398] Furthermore, when a sensor portion is formed on a substrate atthe same time as a display portion, a process of manufacturing an ELdisplay has only an additional step of forming the light receivingdiode, compared to a case of not forming the sensor portion. It istherefore not necessary to have a considerable increase in the number ofmanufacturing steps, and it is possible to suppress the number ofmanufacturing processes.

[0399] Note that by using a portion of the display portion as the sensorportion, the space for forming the sensor portion can be curtailedcompared to a case of not including the sensor portion in the displayportion, and therefore the size of the EL display can be reduced.

What is claimed is:
 1. A semiconductor display device having a displayportion and a sensor portion, wherein: said display portion includes aplurality of display pixels; said sensor portion includes at least onesensor pixel; each of said plurality of display pixels and said sensorpixel has an EL element; said sensor pixel has a light receiving diode;and a luminance of each of the EL elements in said plurality of displaypixels is controlled by the amount of a current flowing in said lightreceiving diode.
 2. A semiconductor display device according to claim 1,wherein said EL element emits the color red, green, or blue.
 3. Asemiconductor display device according to claim 1, wherein said ELelement comprises an anode, a cathode, and an EL layer sandwichedtherebetween, and wherein said EL layer comprises a low molecularorganic material or a polymer organic material.
 4. A semiconductordisplay device according to claim 3, wherein said low molecular organicmaterial is made of Alq₃ (tris-8-quinolilite-aluminum) or TPD(triphenylamine derivative).
 5. A semiconductor display device accordingto claim 3, wherein said polymer organic material is made of PPV(polyphenylene vinylene), PVK (polyvinyl carbazole), or polycarbonate.6. A semiconductor display device according to claim 1, wherein saidsemiconductor display device is incorporated into an electronic deviceselected from the group consisting of a video camera, a digital camera,a goggle type display, a car navigation system, an audio reproducingsystem, a notebook personal computer, a game equipment, a portableinformation terminal and an image playback device.
 7. A semiconductordisplay device having a display portion and a sensor portion, wherein:said display portion includes a plurality of display pixels; said sensorportion includes at least one sensor pixel; each of said plurality ofdisplay pixels and said sensor pixel has a switching TFT, an EL drivingTFT, and an EL element; said sensor pixel has a reset TFT, a buffer TFT,and a light receiving diode; a drive of said EL driving TFT iscontrolled by said switching TFT; a luminescence of said EL element iscontrolled by said EL driving TFT; said buffer TFT has a gate electrode,a source region connected to a constant-current power source, and adrain region held at a fixed electric potential; an electric potentialof said gate electrode and an electric potential of said drain regionbecome equivalent when said reset TFT is ON; and a luminance of each ofthe EL elements in said plurality of display pixels is controlled by achange in an electric potential of said gate electrode in response to acurrent flowing in said light receiving diode when said reset TFT isOFF.
 8. A semiconductor display device according to claim 7, whereinsaid EL element emits the color red, green, or blue.
 9. A semiconductordisplay device according to claim 7, wherein said reset TFT is ann-channel TFT and said buffer TFT is a p-channel TFT.
 10. Asemiconductor display device according to claim 7, wherein said resetTFT is a p-channel TFT and said buffer TFT is an n-channel TFT.
 11. Asemiconductor display device according to claim 7, wherein said ELelement comprises an anode, a cathode, and an EL layer sandwichedtherebetween, and wherein said EL layer comprises a low molecularorganic material or a polymer organic material.
 12. A semiconductordisplay device according to claim 11, wherein said low molecular organicmaterial is made of Alq₃ (tris-8-quinolilite-aluminum) or TPD(triphenylamine derivative).
 13. A semiconductor display deviceaccording to claim 11, wherein said polymer organic material is made ofPPV (polyphenylene vinylene), PVK (polyvinyl carbazole), orpolycarbonate.
 14. A semiconductor display device according to claim 7,wherein said semiconductor display device is incorporated into anelectronic device selected from the group consisting of a video camera,a digital camera, a goggle type display, a car navigation system, anaudio reproducing system, a notebook personal computer, a gameequipment, a portable information terminal and an image playback device.15. A semiconductor display device having a display portion, a sensorportion, a source signal line driver circuit, and a gate signal linedriver circuit, wherein: said display portion includes a plurality ofdisplay pixels; said sensor portion includes at least one sensor pixel;each of said plurality of display pixels and said sensor pixel has aswitching TFT, an EL driving TFT, and an EL element; said sensor pixelhas a reset TFT, a buffer TFT, and a light receiving diode; a drive ofsaid switching TFT is controlled by a signal that is fed to a gateelectrode of said switching TFT from said gate signal line drivercircuit; a drive of said EL driving TFT is controlled by a signal thatis fed to a gate electrode of said EL driving TFT via said switching TFTfrom said source signal line driver circuit; a luminescence of said ELelement is controlled by said EL driving TFT; said buffer TFT has a gateelectrode, a source region connected to a constant-current power source,and a drain region held at a fixed electric potential; an electricpotential of said gate electrode and an electric potential of said drainregion become equivalent when said reset TFT is ON; and a luminance ofeach of the EL elements in said plurality of display pixels iscontrolled by a change in an electric potential of said gate electrodein response to a current flowing in said light receiving diode when saidreset TFT is OFF.
 16. A semiconductor display device according to claim15, wherein said EL element emits the color red, green, or blue.
 17. Asemiconductor display device according to claim 15, wherein said resetTFT is an n-channel TFT and said buffer TFT is a p-channel TFT.
 18. Asemiconductor display device according to claim 15, wherein said resetTFT is a p-channel TFT and said buffer TFT is an n-channel TFT.
 19. Asemiconductor display device according to claim 15, wherein said ELelement comprises an anode, a cathode, and an EL layer sandwichedtherebetween, and wherein said EL layer comprises a low molecularorganic material or a polymer organic material.
 20. A semiconductordisplay device according to claim 19, wherein said low molecular organicmaterial is made of Alq₃ (tris-8-quinolilite-aluminum) or TPD(triphenylamine derivative).
 21. A semiconductor display deviceaccording to claim 19, wherein said polymer organic material is made ofPPV (polyphenylene vinylene), PVK (polyvinyl carbazole), orpolycarbonate.
 22. A semiconductor display device according to claim 15,wherein said semiconductor display device is incorporated into anelectronic device selected from the group consisting of a video camera,a digital camera, a goggle type display, a car navigation system, anaudio reproducing system, a notebook personal computer, a gameequipment, a portable information terminal and an image playback device.23. A semiconductor display device having a display portion and a sensorportion, wherein: said display portion includes a plurality of displaypixels; said sensor portion includes at least one sensor pixel; each ofsaid plurality of display pixels and sensor pixel has a switching TFT,an EL driving TFT, and an EL element; said sensor pixel has a reset TFT,a buffer TFT, and a sensor TFT; a drive of said EL driving TFT iscontrolled by said switching TFT; a luminescence of said EL element iscontrolled by said EL driving TFT; said sensor TFT is constantly OFF;said buffer TFT has a gate electrode, a source region that is connectedto a constant-current source, and a drain region that is held at a fixedelectric potential; an electric potential of said gate electrode and anelectric potential of said drain region become equivalent when saidreset TFT is ON; and a luminance of each of the EL elements in saidplurality of display pixels is controlled by a change in an electricpotential of said gate electrode in response to an off current flowingin said sensor TFT when said reset TFT is OFF.
 24. A semiconductordisplay device according to claim 23, wherein said EL element emits thecolor red, green, or blue.
 25. A semiconductor display device accordingto claim 23, wherein said reset TFT is an n-channel TFT, said buffer TFTis a p-channel TFT, and said sensor TFT is a p-channel TFT.
 26. Asemiconductor display device according to claim 23, wherein said resetTFT is a p-channel TFT, said buffer TFT is an n-channel TFT, and saidsensor TFT is an n-channel TFT.
 27. A semiconductor display deviceaccording to claim 23, wherein said EL element comprises an anode, acathode, and an EL layer sandwiched therebetween, and wherein said ELlayer comprises a low molecular organic material or a polymer organicmaterial.
 28. A semiconductor display device according to claim 27,wherein said low molecular organic material is made of Alq₃(tris-8-quinolilite-aluminum) or TPD (triphenylamine derivative).
 29. Asemiconductor display device according to claim 27, wherein said polymerorganic material is made of PPV (polyphenylene vinylene), PVK (polyvinylcarbazole), or polycarbonate.
 30. A semiconductor display deviceaccording to claim 23, wherein said semiconductor display device isincorporated into an electronic device selected from the groupconsisting of a video camera, a digital camera, a goggle type display, acar navigation system, an audio reproducing system, a notebook personalcomputer, a game equipment, a portable information terminal and an imageplayback device.
 31. A semiconductor display device having a displayportion, a sensor portion, a source signal line driver circuit, and agate signal line driver circuit, wherein: said display portion includesa plurality of display pixels; said sensor portion includes at least onesensor pixel; each of said plurality of display pixels and said sensorpixel has a switching TFT, an EL driving TFT, and an EL element; saidsensor pixel has a reset TFT, a buffer TFT, and a sensor TFT; saidswitching TFT is driven by a signal that is fed to a gate electrode ofsaid switching TFT from said gate signal line driver circuit; a drive ofsaid EL driving TFT is controlled by a signal that is fed to a gateelectrode of said EL driving TFT via said switching TFT from said sourcesignal line driver circuit; a luminescence of said EL element iscontrolled by said EL driving TFT; said sensor TFT is constantly OFF;said buffer TFT has a gate electrode, a source region that is connectedto a constant-current power source, and a drain region that is held at afixed electric potential; an electric potential of said gate electrodeand an electric potential of said drain region become equivalent whensaid reset TFT is ON; and a luminance of each of the EL elements in saidplurality of display pixels is controlled by a change in an electricpotential of said gate electrode in response to an off current flowingin said sensor TFT when said reset TFT is OFF.
 32. A semiconductordisplay device according to claim 31, wherein said EL element emits thecolor red, green, or blue.
 33. A semiconductor display device accordingto claim 31, wherein said reset TFT is an n-channel TFT, said buffer TFTis a p-channel TFT, and said sensor TFT is a p-channel TFT.
 34. Asemiconductor display device according to claim 31, wherein said resetTFT is a p-channel TFT, said buffer TFT is an n-channel TFT, and saidsensor TFT is an n-channel TFT.
 35. A semiconductor display deviceaccording to claim 31, wherein said EL element comprises an anode, acathode, and an EL layer sandwiched therebetween, and wherein said ELlayer comprises a low molecular organic material or a polymer organicmaterial.
 36. A semiconductor display device according to claim 35,wherein said low molecular organic material is made of Alq₃(tris-8-quinolilite-aluminum) or TPD (triphenylamine derivative).
 37. Asemiconductor display device according to claim 35, wherein said polymerorganic material is made of PPV (polyphenylene vinylene), PVK (polyvinylcarbazole), or polycarbonate.
 38. A semiconductor display deviceaccording to claim 31, wherein said semiconductor display device isincorporated into an electronic device selected from the groupconsisting of a video camera, a digital camera, a goggle type display, acar navigation system, an audio reproducing system, a notebook personalcomputer, a game equipment, a portable information terminal and an imageplayback device.